Re: 900 GTO tracking problem


Feb 26 7:15 AM

 


----------------------------

#4395 Feb 26 7:15 AM

Hi,



My 900GTO seemed to track fine when using a scope with a 700 mm FL (2.65

arc-sec/pixel). At that FL, the scope load resulted in a single 18-pound

counterweight near the top of the shaft. I have recently gone to a longer

FL of 1800 mm (1.02 arc-sec./pixel) and am having significant problems. Now

the load is balanced by 2 18-pound counterweights approximately 2/3 of the

way down the shaft. I did expect it to be more difficult but I haven't been

successful thus far and am looking for advice.



The DEC axis tracks fine, holding within 0.4 pixels on the tracking CCD of

an ST-8E. I have 0 backlash set by the hand controller but have set it to 1

for Maxim calibration to get good calibration symmetry in the Y direction.

By my calculations, this is around 1.8 arc-sec./pixel. The RA axis (1.6

arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak. I

would expect any seeing issue to be symmetrical. Here is a typical image of

a few minutes of tracking:



www.hiddenloft.darkhorizons.org/guide.jpg



I am using MaximDL v3.05 for CCD control. The camera axes are parallel to

RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at 0.5x,

calibrating and guiding at 0.5x, calibrating and guiding at 1x. I have

tried guiding exposures from 4 to 8 seconds, always making sure the guide

star is no more than 30k. I have tried making the mount "heavy east" to the

tune of 30-40 inch-pounds. I have tried different parts of the sky with

similar results. I have checked the RA backlash according to the AP web

site. While jiggling the counterweight shaft I wasn't sure I could detect

any movement. I rotationally jiggled (does that make sense?) the brass

shaft extension and felt a little play and heard a clicking noise so I

slightly adjusted the gear engagement. This didn't seem to make any

improvement.



With this level of tracking performance, a 120 second guided exposure gives

stars elongated in the RA direction. Polar alignment is fairly close,

certainly within 1 arc-minute. I know the mount is capable of better

performance than I am getting and am certain it is cockpit error. I'm just

running out of things to try and would welcome any hints or advice.



Thanks,



John

www.hiddenloft.darkhorizons.org/



----------------------------

#4396 Feb 26 7:59 AM

John,



What guide rate are you using? How often does the mount correct? I assume

you are using the tracking chip in the ST8?

When at Sunglow I used my ST5c on a separated guide scope and it worked

fine. I guess beginners luck. I tracked or corrected at 1x calibrated at 1x

and updated each second which may have been too often but it was working so

I did not try to fix it.g> It tracked for hours that way. I remember my

FWHM was quit large (8) but it held the star spot on. I was able to hold

round stars for 10 min unguided so I had good polar alignment.



It sounds like you are doing everything right. What happens when you shorten

the tracking interval?



Not much help but maybe trigered the old brain cells.....

Andy



-----Original Message-----

From: John Smith [mailto:johnzonie@...]

Sent: Tuesday, February 26, 2002 7:16 AM

To: Ap-Gto

Subject: [ap-gto] 900 GTO tracking problem





Hi,



My 900GTO seemed to track fine when using a scope with a 700 mm FL (2.65

arc-sec/pixel). At that FL, the scope load resulted in a single 18-pound

counterweight near the top of the shaft. I have recently gone to a longer

FL of 1800 mm (1.02 arc-sec./pixel) and am having significant problems. Now

the load is balanced by 2 18-pound counterweights approximately 2/3 of the

way down the shaft. I did expect it to be more difficult but I haven't been

successful thus far and am looking for advice.



The DEC axis tracks fine, holding within 0.4 pixels on the tracking CCD of

an ST-8E. I have 0 backlash set by the hand controller but have set it to 1

for Maxim calibration to get good calibration symmetry in the Y direction.

By my calculations, this is around 1.8 arc-sec./pixel. The RA axis (1.6

arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak. I

would expect any seeing issue to be symmetrical. Here is a typical image of

a few minutes of tracking:



www.hiddenloft.darkhorizons.org/guide.jpg



I am using MaximDL v3.05 for CCD control. The camera axes are parallel to

RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at 0.5x,

calibrating and guiding at 0.5x, calibrating and guiding at 1x. I have

tried guiding exposures from 4 to 8 seconds, always making sure the guide

star is no more than 30k. I have tried making the mount "heavy east" to the

tune of 30-40 inch-pounds. I have tried different parts of the sky with

similar results. I have checked the RA backlash according to the AP web

site. While jiggling the counterweight shaft I wasn't sure I could detect

any movement. I rotationally jiggled (does that make sense?) the brass

shaft extension and felt a little play and heard a clicking noise so I

slightly adjusted the gear engagement. This didn't seem to make any

improvement.



With this level of tracking performance, a 120 second guided exposure gives

stars elongated in the RA direction. Polar alignment is fairly close,

certainly within 1 arc-minute. I know the mount is capable of better

performance than I am getting and am certain it is cockpit error. I'm just

running out of things to try and would welcome any hints or advice.



Thanks,



John

www.hiddenloft.darkhorizons.org/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#4397 Feb 26 8:32 AM

In a message dated 2/26/2002 7:16:54 AM Pacific Standard Time,

johnzonie@... writes:



> The RA axis (1.6

> arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak, I

am using MaximDL v3.05 for CCD control. >>



I am not a fan of MaximDL for tracking. I have never been able to

successfully guide with this program. Have you tried going back to the

fundamentals and tracking with your CCDOPS program?



RA should always guide better than DEC since all you are doing is slowing

down and speeding up the sidereal tracking rate - you are never reversing the

motors or introducing any kind of backlash delay. To allow you to understand

where the problem might be coming from, try guiding on a star with your own

eye and a high power crosshair eyepiece. Can you guide in RA and have a very

fine level of control of the star as you push the buttons? You will find that

for RA, you can move the star and control it perfectly without any kind of

delay. once you prove this to yourself, you can go to autoguide (assuming you

have found no obvious defect in the RA axis). Long shot - one thing that can

affect the RA tracking is having the clutches too loose and the RA shaft

damper too tight. Check to be sure that the clutch is not slipping, then back

off the shaft damper completely to see if this gives any improvement.



For autoguiding, my favorite program now is CCDSoft. With this program, I can

see the guide parameters, and be able to tell whether they make sense after

doing a calibration run. I can change the agressiveness setting and make

other improvements that allow the mount to guide in a stable manner.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4398 Feb 26 10:20 AM

Thanks for the hints, Roland. I was surprised about the RA being worse than

DEC as well. I do have CCDSoft and I'll give that a try. I know the

clutches are secure but I had been keeping the dampers snug. I'll try

loosening them and see what happens tonight. Full moon time makes equipment

adjusting time well spent g> When you are guiding with one of your long FL

scopes, do you recall what kind of guiding errors you see? I know that is

an open ended question but just curious. Also, where to you tend to operate

CCDSoft aggressiveness?



Thanks,



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: chris1011@... [mailto:chris1011@...]

Sent: Tuesday, February 26, 2002 9:33 AM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 900 GTO tracking problem



In a message dated 2/26/2002 7:16:54 AM Pacific Standard Time,

johnzonie@... writes:



> The RA axis (1.6

> arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak, I

am using MaximDL v3.05 for CCD control. >>



I am not a fan of MaximDL for tracking. I have never been able to

successfully guide with this program. Have you tried going back to the

fundamentals and tracking with your CCDOPS program?



RA should always guide better than DEC since all you are doing is slowing

down and speeding up the sidereal tracking rate - you are never reversing

the

motors or introducing any kind of backlash delay. To allow you to understand

where the problem might be coming from, try guiding on a star with your own

eye and a high power crosshair eyepiece. Can you guide in RA and have a very

fine level of control of the star as you push the buttons? You will find

that

for RA, you can move the star and control it perfectly without any kind of

delay. once you prove this to yourself, you can go to autoguide (assuming

you

have found no obvious defect in the RA axis). Long shot - one thing that can

affect the RA tracking is having the clutches too loose and the RA shaft

damper too tight. Check to be sure that the clutch is not slipping, then

back

off the shaft damper completely to see if this gives any improvement.



For autoguiding, my favorite program now is CCDSoft. With this program, I

can

see the guide parameters, and be able to tell whether they make sense after

doing a calibration run. I can change the agressiveness setting and make

other improvements that allow the mount to guide in a stable manner.



Roland Christen





[Non-text portions of this message have been removed]







To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/



----------------------------

#4399 Feb 26 10:22 AM

Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am using the

guide chip in the ST8. The mount seems to correct after every exposure.

I've tried guiding intervals of 4 and 8 seconds. Your 155 has an FL of 1085

mm, closer to my 700 mm experience, which was fine. I'm having trouble at

the longer FL's.



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: Andy Forsberg [mailto:CS-Imaging@...]

Sent: Tuesday, February 26, 2002 9:00 AM

To: ap-gto@yahoogroups.com

Subject: RE: [ap-gto] 900 GTO tracking problem



John,



What guide rate are you using? How often does the mount correct? I assume

you are using the tracking chip in the ST8?

When at Sunglow I used my ST5c on a separated guide scope and it worked

fine. I guess beginners luck. I tracked or corrected at 1x calibrated at 1x

and updated each second which may have been too often but it was working so

I did not try to fix it.g> It tracked for hours that way. I remember my

FWHM was quit large (8) but it held the star spot on. I was able to hold

round stars for 10 min unguided so I had good polar alignment.



It sounds like you are doing everything right. What happens when you shorten

the tracking interval?



Not much help but maybe trigered the old brain cells.....

Andy



-----Original Message-----

From: John Smith [mailto:johnzonie@...]

Sent: Tuesday, February 26, 2002 7:16 AM

To: Ap-Gto

Subject: [ap-gto] 900 GTO tracking problem





Hi,



My 900GTO seemed to track fine when using a scope with a 700 mm FL (2.65

arc-sec/pixel). At that FL, the scope load resulted in a single 18-pound

counterweight near the top of the shaft. I have recently gone to a longer

FL of 1800 mm (1.02 arc-sec./pixel) and am having significant problems. Now

the load is balanced by 2 18-pound counterweights approximately 2/3 of the

way down the shaft. I did expect it to be more difficult but I haven't been

successful thus far and am looking for advice.



The DEC axis tracks fine, holding within 0.4 pixels on the tracking CCD of

an ST-8E. I have 0 backlash set by the hand controller but have set it to 1

for Maxim calibration to get good calibration symmetry in the Y direction.

By my calculations, this is around 1.8 arc-sec./pixel. The RA axis (1.6

arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak. I

would expect any seeing issue to be symmetrical. Here is a typical image of

a few minutes of tracking:



www.hiddenloft.darkhorizons.org/guide.jpg



I am using MaximDL v3.05 for CCD control. The camera axes are parallel to

RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at 0.5x,

calibrating and guiding at 0.5x, calibrating and guiding at 1x. I have

tried guiding exposures from 4 to 8 seconds, always making sure the guide

star is no more than 30k. I have tried making the mount "heavy east" to the

tune of 30-40 inch-pounds. I have tried different parts of the sky with

similar results. I have checked the RA backlash according to the AP web

site. While jiggling the counterweight shaft I wasn't sure I could detect

any movement. I rotationally jiggled (does that make sense?) the brass

shaft extension and felt a little play and heard a clicking noise so I

slightly adjusted the gear engagement. This didn't seem to make any

improvement.



With this level of tracking performance, a 120 second guided exposure gives

stars elongated in the RA direction. Polar alignment is fairly close,

certainly within 1 arc-minute. I know the mount is capable of better

performance than I am getting and am certain it is cockpit error. I'm just

running out of things to try and would welcome any hints or advice.



Thanks,



John

www.hiddenloft.darkhorizons.org/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#4400 Feb 26 10:59 AM

In a message dated 2/26/2002 10:23:49 AM Pacific Standard Time,

johnzonie@... writes:



> I know the

> clutches are secure but I had been keeping the dampers snug. I'll try

> loosening them and see what happens tonight. Full moon time makes

> equipment

> adjusting time well spent g> When you are guiding with one of your long FL

> scopes, do you recall what kind of guiding errors you see? I know that is

> an open ended question but just curious. Also, where to you tend to

> operate

> CCDSoft aggressiveness?

>



Just loosen the RA damper knob. Worth a try but I doubt that this would do

anything for short period guiding, it may have a small effect for hour long

unguided exposures.



With 146 inches of focal length, I get guiding excursions of 1.5 pixels or

less. This is totally random and is due to atmospheric motions. When the

atmosphere is really steady, I can turn the agressiveness up to 1 and the

guiding is a fraction of a pixel. In unsteady seeing I would go down to .7 or

less. What is important is that your guiding parameter numbers be realistic.

In each axis they should be similar. For instance, if the RA numbers are 10

and 9.8, that's fine. If they are 10 and 4, this signals trouble. The lower

the number, the higher the loop gain will be. Very low numbers will cause the

camera guider to send very long "button pushes" to the mount for small

excursions of the guide star. The larger the number, the shorter is the

correction signal or "button push" time. make sure that you don't have too

high a minimum on time. Min on time should be 50msec or less. Long button

pushes lead inevitably to overshoot of the guide star and a "hunting" back

and forth. It is important to keep your loop gain as low as possible while

still being able to follow the slow drift motions of the guide star (drift

due to PE and polar misalignment). For instance, If you are set up for 5

second integration times and your typical drift is 1/4 pixel per 5 second

time period, there is no reason why the guider should be set up to ever send

a correction signal of 2 or 3 pixels. The atmosphere may be moving the star

by 1 or 2 pixels between sessions, but this must be ignored by the software.

It is too late to correct for an atmospheric random motion after the fact,

because by the time you actually send the correction signal, the guide star

has probably moved the other way already.



So, to summarize: 1) make sure the parameter numbers are similar for each

axis, and not too small. For long focus scopes, a number of 3 would be

considered small, 10 or larger would be better for a 5 second cal run.

2) keep the loop gain down, either by increasing

the parameter numbers in the unstable axis, or by decreasing the

agressiveness for overall stability.

3) keep min "on" time below 50msec

4) don't try to chase the seeing



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4401 Feb 26 11:11 AM

In a message dated 2/26/2002 10:23:49 AM Pacific Standard Time,

johnzonie@... writes:



> I do have CCDSoft and I'll give that a try.



While you are at it, try running 30 or so exposures withTrack&Accumulate in

CCDOPS with 3 to 5 second exposure times. The resultant chart will tell you a

lot about the tracking of RA and drift due to PE and polar misalignment.

Doing this also helps me to troubleshoot equipment that I cannot physically

see myself. Everyone should do this before launching on any imaging project

just so you know what these numbers are.



One more thing which is very important, you must have a stable camera to

telescope connection. If anything moves during a guiding session relative to

the optics, you will get poor guiding. Make sure the cords are securely tied

to the mount before they are allowed to droop down to the ground. Cords that

pull on the camera during the exposure can mess things up. Are your optics

stable within the mechanical tube, or do they flop around? Is there a fan on

your system somewhere that is vibrating the setup? I've even had problems

with the built-in fan on my ST10E in certain orientation. I get severely

elongated stars. I had to remove the fan and place some vibration absorbing

material between fan and camera body. One way to tell is to turn off the fan

and do a short run.



Roland Christen



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4402 Feb 26 1:06 PM

Thanks for all the hints, Roland. My work is cut out for me tonight! My

ST-8E is T-thread mounted to an ADA-204 and thence to the AP focuser, so

that should be pretty solid. I like your comments about loop gain. As an

old E.E., that makes all the sense in the world. I'll also give CCDops a

whirl. I tried that once before but didn't RTFM enough and was only able to

get a small number of exposures. I'll report back once I have something

significant.



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: chris1011@... [mailto:chris1011@...]

Sent: Tuesday, February 26, 2002 12:11 PM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 900 GTO tracking problem



In a message dated 2/26/2002 10:23:49 AM Pacific Standard Time,

johnzonie@... writes:



> I do have CCDSoft and I'll give that a try.



While you are at it, try running 30 or so exposures withTrack&Accumulate in

CCDOPS with 3 to 5 second exposure times. The resultant chart will tell you

a

lot about the tracking of RA and drift due to PE and polar misalignment.

Doing this also helps me to troubleshoot equipment that I cannot physically

see myself. Everyone should do this before launching on any imaging project

just so you know what these numbers are.



One more thing which is very important, you must have a stable camera to

telescope connection. If anything moves during a guiding session relative to

the optics, you will get poor guiding. Make sure the cords are securely tied

to the mount before they are allowed to droop down to the ground. Cords that

pull on the camera during the exposure can mess things up. Are your optics

stable within the mechanical tube, or do they flop around? Is there a fan on

your system somewhere that is vibrating the setup? I've even had problems

with the built-in fan on my ST10E in certain orientation. I get severely

elongated stars. I had to remove the fan and place some vibration absorbing

material between fan and camera body. One way to tell is to turn off the fan

and do a short run.



Roland Christen



Roland Christen





[Non-text portions of this message have been removed]







To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#4403 Feb 26 1:07 PM

Hi John,



It gets worse, I was guiding with my 80mm/900mm AP guide scope which is evan

shorter in the region where you are NOT having problems. I'll have to try

it with my C11 2800mm and see if I have problems.

I guess I'm not much help since I have not tried it at the longer FL. Doug G

told me to always calibrate at 1x. I'm not sure if he was thinking in terms

of focal length when he gave that advice because he knew what I was using at

the time.



Wish I could know all the answers. Then I'd have to write a book.



Oh by the way I ordered a FLI CM10 2ME Maxcam. Will use the ST5c for

Guiding.



Take care Andy



-----Original Message-----

From: John Smith [mailto:johnzonie@...]

Sent: Tuesday, February 26, 2002 10:23 AM

To: ap-gto@yahoogroups.com

Subject: RE: [ap-gto] 900 GTO tracking problem





Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am using the

guide chip in the ST8. The mount seems to correct after every exposure.

I've tried guiding intervals of 4 and 8 seconds. Your 155 has an FL of 1085

mm, closer to my 700 mm experience, which was fine. I'm having trouble at

the longer FL's.



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: Andy Forsberg [mailto:CS-Imaging@...]

Sent: Tuesday, February 26, 2002 9:00 AM

To: ap-gto@yahoogroups.com

Subject: RE: [ap-gto] 900 GTO tracking problem



John,



What guide rate are you using? How often does the mount correct? I assume

you are using the tracking chip in the ST8?

When at Sunglow I used my ST5c on a separated guide scope and it worked

fine. I guess beginners luck. I tracked or corrected at 1x calibrated at 1x

and updated each second which may have been too often but it was working so

I did not try to fix it.g> It tracked for hours that way. I remember my

FWHM was quit large (8) but it held the star spot on. I was able to hold

round stars for 10 min unguided so I had good polar alignment.



It sounds like you are doing everything right. What happens when you shorten

the tracking interval?



Not much help but maybe trigered the old brain cells.....

Andy



-----Original Message-----

From: John Smith [mailto:johnzonie@...]

Sent: Tuesday, February 26, 2002 7:16 AM

To: Ap-Gto

Subject: [ap-gto] 900 GTO tracking problem





Hi,



My 900GTO seemed to track fine when using a scope with a 700 mm FL (2.65

arc-sec/pixel). At that FL, the scope load resulted in a single 18-pound

counterweight near the top of the shaft. I have recently gone to a longer

FL of 1800 mm (1.02 arc-sec./pixel) and am having significant problems. Now

the load is balanced by 2 18-pound counterweights approximately 2/3 of the

way down the shaft. I did expect it to be more difficult but I haven't been

successful thus far and am looking for advice.



The DEC axis tracks fine, holding within 0.4 pixels on the tracking CCD of

an ST-8E. I have 0 backlash set by the hand controller but have set it to 1

for Maxim calibration to get good calibration symmetry in the Y direction.

By my calculations, this is around 1.8 arc-sec./pixel. The RA axis (1.6

arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-peak. I

would expect any seeing issue to be symmetrical. Here is a typical image of

a few minutes of tracking:



www.hiddenloft.darkhorizons.org/guide.jpg



I am using MaximDL v3.05 for CCD control. The camera axes are parallel to

RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at 0.5x,

calibrating and guiding at 0.5x, calibrating and guiding at 1x. I have

tried guiding exposures from 4 to 8 seconds, always making sure the guide

star is no more than 30k. I have tried making the mount "heavy east" to the

tune of 30-40 inch-pounds. I have tried different parts of the sky with

similar results. I have checked the RA backlash according to the AP web

site. While jiggling the counterweight shaft I wasn't sure I could detect

any movement. I rotationally jiggled (does that make sense?) the brass

shaft extension and felt a little play and heard a clicking noise so I

slightly adjusted the gear engagement. This didn't seem to make any

improvement.



With this level of tracking performance, a 120 second guided exposure gives

stars elongated in the RA direction. Polar alignment is fairly close,

certainly within 1 arc-minute. I know the mount is capable of better

performance than I am getting and am certain it is cockpit error. I'm just

running out of things to try and would welcome any hints or advice.



Thanks,



John

www.hiddenloft.darkhorizons.org/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/









To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#4404 Feb 26 1:43 PM

In message 28.22a20059.29ad12af@...>, chris1011@... writes >I am not a fan of MaximDL for tracking. I have never been able to

>successfully guide with this program. Have you tried going back to the

>fundamentals and tracking with your CCDOPS program?



Interesting, I thought I was the only one with this problem. There are a

lot of CCD imagers using it successfully out there. I have problems with

DEC tracking, it seems to wander off and take a long time to return to

the designated tracking pixel. My latest though was could it be a bug

when you set the DEC of an object for calibration then guiding?



This may be a little off topic, so happy to take it off line..



Adrian

>

>RA should always guide better than DEC since all you are doing is slowing

>down and speeding up the sidereal tracking rate - you are never reversing the

>motors or introducing any kind of backlash delay. To allow you to understand

>where the problem might be coming from, try guiding on a star with your own

>eye and a high power crosshair eyepiece. Can you guide in RA and have a very

>fine level of control of the star as you push the buttons? You will find that

>for RA, you can move the star and control it perfectly without any kind of

>delay. once you prove this to yourself, you can go to autoguide (assuming you

>have found no obvious defect in the RA axis). Long shot - one thing that can

>affect the RA tracking is having the clutches too loose and the RA shaft

>damper too tight. Check to be sure that the clutch is not slipping, then back

>off the shaft damper completely to see if this gives any improvement.

>

>For autoguiding, my favorite program now is CCDSoft. With this program, I can

>see the guide parameters, and be able to tell whether they make sense after

>doing a calibration run. I can change the agressiveness setting and make

>other improvements that allow the mount to guide in a stable manner.

>

>Roland Christen

>

>

>[Non-text portions of this message have been removed]

>

>

>

>To UNSUBSCRIBE, or for general information on the ap-gto list

>see groups.yahoo.com/group/ap-gto

>

>Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>





Adrian Catterall

CCD Astronomer

Guilden Morden

Herts



Web page: www.observatory.demon.co.uk

Mail: catterall@...



----------------------------

#4406 Feb 26 1:49 PM

Hi John,



Roland (as usual) has given some pretty good advice. I had a phone

conversation with him about guiding, in general, and he also

explained the benefits that the additional "options" available in

CCDsoft have over Maxim. At this point, I still use Maxim for

guiding because I get reasonable results (and don't have CCDsoft as

an option..I'm hoping Maxim will incorporate more control features in

the guide options when they do further upgrades)



As a point of reference, using Maxim, I find that on "average" nights

I get peak to peak variations of 1.5 to 2 pixels (guide chip) when

using 4 to 8 sec. guide exposures at 1800mm (C11 at F6.3) NOTE: my

seeing is not great here! On exceptional nights, I can get peak to

peak of under 1 pixel (no more than .5 in either direction)...these

nights are rare here.



Roland once pointed out that sometimes seeing/atmospheric movements

can occur mostly in one direction. Seems odd, but I found it to be

true...on a night of poor seeing, where one axis didn't perform as

well as the other, I rotated the camera 90deg. and sure enough,

the "new" x axis became the one performing poorly. I guess there are

times when "seeing" errors are not completely random. (Just

something to consider while testing).



Good luck tonight!



Randy Nulman

--- In ap-gto@y..., "John Smith" johnzonie@e...> wrote:

> Thanks for all the hints, Roland. My work is cut out for me

tonight! My

> ST-8E is T-thread mounted to an ADA-204 and thence to the AP

focuser, so

> that should be pretty solid. I like your comments about loop

gain. As an

> old E.E., that makes all the sense in the world. I'll also give

CCDops a

> whirl. I tried that once before but didn't RTFM enough and was

only able to

> get a small number of exposures. I'll report back once I have

something

> significant.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: chris1011@a... [mailto:chris1011@a...]

> Sent: Tuesday, February 26, 2002 12:11 PM

> To: ap-gto@y...

> Subject: Re: [ap-gto] 900 GTO tracking problem

>

> In a message dated 2/26/2002 10:23:49 AM Pacific Standard Time,

> johnzonie@e... writes:

>

>

> > I do have CCDSoft and I'll give that a try.

>

> While you are at it, try running 30 or so exposures

withTrack&Accumulate in

> CCDOPS with 3 to 5 second exposure times. The resultant chart will

tell you

> a

> lot about the tracking of RA and drift due to PE and polar

misalignment.

> Doing this also helps me to troubleshoot equipment that I cannot

physically

> see myself. Everyone should do this before launching on any imaging

project

> just so you know what these numbers are.

>

> One more thing which is very important, you must have a stable

camera to

> telescope connection. If anything moves during a guiding session

relative to

> the optics, you will get poor guiding. Make sure the cords are

securely tied

> to the mount before they are allowed to droop down to the ground.

Cords that

> pull on the camera during the exposure can mess things up. Are your

optics

> stable within the mechanical tube, or do they flop around? Is there

a fan on

> your system somewhere that is vibrating the setup? I've even had

problems

> with the built-in fan on my ST10E in certain orientation. I get

severely

> elongated stars. I had to remove the fan and place some vibration

absorbing

> material between fan and camera body. One way to tell is to turn

off the fan

> and do a short run.

>

> Roland Christen

>

> Roland Christen

>

>

> [Non-text portions of this message have been removed]

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







----------------------------

#4407 Feb 26 2:15 PM

Hi Andy,



I believe it's completely possible to *calibrate* and guide at .5x

_IF_ you _accurately_ compensate for backlash during the calibrate

routine...backlash will become much more of an issue at .5x than 1x.



I verify my backlash settings (dec) by doing the following:



During a calibration test, I determine that my initial dec. move

closely matches my RA move (in pixels). Then I look to see if the

movement "back" in dec. puts me within 1 pixel of my intitial

starting point. If so, I begin the guide routine...if not, I adjust

backlash until I get the desired response. (I have found that

different "pointing" postions of the mount will have an affect on the

final results..so I always test the backlash for the _area_ I'm

imaging in)



Randy





--- In ap-gto@y..., "Andy Forsberg" CS-Imaging@p...> wrote:

> Hi John,

>

> It gets worse, I was guiding with my 80mm/900mm AP guide scope

which is evan

> shorter in the region where you are NOT having problems. I'll have

to try

> it with my C11 2800mm and see if I have problems.

> I guess I'm not much help since I have not tried it at the longer

FL. Doug G

> told me to always calibrate at 1x. I'm not sure if he was thinking

in terms

> of focal length when he gave that advice because he knew what I was

using at

> the time.

>

> Wish I could know all the answers. Then I'd have to write a book.

>

> Oh by the way I ordered a FLI CM10 2ME Maxcam. Will use the ST5c

for

> Guiding.

>

> Take care Andy

>

> -----Original Message-----

> From: John Smith [mailto:johnzonie@e...]

> Sent: Tuesday, February 26, 2002 10:23 AM

> To: ap-gto@y...

> Subject: RE: [ap-gto] 900 GTO tracking problem

>

>

> Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am

using the

> guide chip in the ST8. The mount seems to correct after every

exposure.

> I've tried guiding intervals of 4 and 8 seconds. Your 155 has an

FL of 1085

> mm, closer to my 700 mm experience, which was fine. I'm having

trouble at

> the longer FL's.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: Andy Forsberg [mailto:CS-Imaging@p...]

> Sent: Tuesday, February 26, 2002 9:00 AM

> To: ap-gto@y...

> Subject: RE: [ap-gto] 900 GTO tracking problem

>

> John,

>

> What guide rate are you using? How often does the mount correct? I

assume

> you are using the tracking chip in the ST8?

> When at Sunglow I used my ST5c on a separated guide scope and it

worked

> fine. I guess beginners luck. I tracked or corrected at 1x

calibrated at 1x

> and updated each second which may have been too often but it was

working so

> I did not try to fix it.g> It tracked for hours that way. I

remember my

> FWHM was quit large (8) but it held the star spot on. I was able

to hold

> round stars for 10 min unguided so I had good polar alignment.

>

> It sounds like you are doing everything right. What happens when

you shorten

> the tracking interval?

>

> Not much help but maybe trigered the old brain cells.....

> Andy

>

> -----Original Message-----

> From: John Smith [mailto:johnzonie@e...]

> Sent: Tuesday, February 26, 2002 7:16 AM

> To: Ap-Gto

> Subject: [ap-gto] 900 GTO tracking problem

>

>

> Hi,

>

> My 900GTO seemed to track fine when using a scope with a 700 mm FL

(2.65

> arc-sec/pixel). At that FL, the scope load resulted in a single 18-

pound

> counterweight near the top of the shaft. I have recently gone to a

longer

> FL of 1800 mm (1.02 arc-sec./pixel) and am having significant

problems. Now

> the load is balanced by 2 18-pound counterweights approximately 2/3

of the

> way down the shaft. I did expect it to be more difficult but I

haven't been

> successful thus far and am looking for advice.

>

> The DEC axis tracks fine, holding within 0.4 pixels on the tracking

CCD of

> an ST-8E. I have 0 backlash set by the hand controller but have

set it to 1

> for Maxim calibration to get good calibration symmetry in the Y

direction.

> By my calculations, this is around 1.8 arc-sec./pixel. The RA axis

(1.6

> arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-

peak. I

> would expect any seeing issue to be symmetrical. Here is a typical

image of

> a few minutes of tracking:

>

> www.hiddenloft.darkhorizons.org/guide.jpg

>

> I am using MaximDL v3.05 for CCD control. The camera axes are

parallel to

> RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at

0.5x,

> calibrating and guiding at 0.5x, calibrating and guiding at 1x. I

have

> tried guiding exposures from 4 to 8 seconds, always making sure the

guide

> star is no more than 30k. I have tried making the mount "heavy

east" to the

> tune of 30-40 inch-pounds. I have tried different parts of the sky

with

> similar results. I have checked the RA backlash according to the

AP web

> site. While jiggling the counterweight shaft I wasn't sure I could

detect

> any movement. I rotationally jiggled (does that make sense?) the

brass

> shaft extension and felt a little play and heard a clicking noise

so I

> slightly adjusted the gear engagement. This didn't seem to make any

> improvement.

>

> With this level of tracking performance, a 120 second guided

exposure gives

> stars elongated in the RA direction. Polar alignment is fairly

close,

> certainly within 1 arc-minute. I know the mount is capable of

better

> performance than I am getting and am certain it is cockpit error.

I'm just

> running out of things to try and would welcome any hints or advice.

>

> Thanks,

>

> John

> www.hiddenloft.darkhorizons.org/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







----------------------------

#4408 Feb 26 2:21 PM

Thanks for the reference points, Randy. Maybe I'm not doing all that badly.

I was expecting both directions to be the same. Apparently not so! That

is fascinating about different seeing in different directions.



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: randy_nulman [mailto:rjnulman@...]

Sent: Tuesday, February 26, 2002 2:50 PM

To: ap-gto@yahoogroups.com

Subject: [ap-gto] Re: 900 GTO tracking problem



Hi John,



Roland (as usual) has given some pretty good advice. I had a phone

conversation with him about guiding, in general, and he also

explained the benefits that the additional "options" available in

CCDsoft have over Maxim. At this point, I still use Maxim for

guiding because I get reasonable results (and don't have CCDsoft as

an option..I'm hoping Maxim will incorporate more control features in

the guide options when they do further upgrades)



As a point of reference, using Maxim, I find that on "average" nights

I get peak to peak variations of 1.5 to 2 pixels (guide chip) when

using 4 to 8 sec. guide exposures at 1800mm (C11 at F6.3) NOTE: my

seeing is not great here! On exceptional nights, I can get peak to

peak of under 1 pixel (no more than .5 in either direction)...these

nights are rare here.



Roland once pointed out that sometimes seeing/atmospheric movements

can occur mostly in one direction. Seems odd, but I found it to be

true...on a night of poor seeing, where one axis didn't perform as

well as the other, I rotated the camera 90deg. and sure enough,

the "new" x axis became the one performing poorly. I guess there are

times when "seeing" errors are not completely random. (Just

something to consider while testing).



Good luck tonight!



Randy Nulman

--- In ap-gto@y..., "John Smith" johnzonie@e...> wrote:

> Thanks for all the hints, Roland. My work is cut out for me

tonight! My

> ST-8E is T-thread mounted to an ADA-204 and thence to the AP

focuser, so

> that should be pretty solid. I like your comments about loop

gain. As an

> old E.E., that makes all the sense in the world. I'll also give

CCDops a

> whirl. I tried that once before but didn't RTFM enough and was

only able to

> get a small number of exposures. I'll report back once I have

something

> significant.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: chris1011@a... [mailto:chris1011@a...]

> Sent: Tuesday, February 26, 2002 12:11 PM

> To: ap-gto@y...

> Subject: Re: [ap-gto] 900 GTO tracking problem

>

> In a message dated 2/26/2002 10:23:49 AM Pacific Standard Time,

> johnzonie@e... writes:

>

>

> > I do have CCDSoft and I'll give that a try.

>

> While you are at it, try running 30 or so exposures

withTrack&Accumulate in

> CCDOPS with 3 to 5 second exposure times. The resultant chart will

tell you

> a

> lot about the tracking of RA and drift due to PE and polar

misalignment.

> Doing this also helps me to troubleshoot equipment that I cannot

physically

> see myself. Everyone should do this before launching on any imaging

project

> just so you know what these numbers are.

>

> One more thing which is very important, you must have a stable

camera to

> telescope connection. If anything moves during a guiding session

relative to

> the optics, you will get poor guiding. Make sure the cords are

securely tied

> to the mount before they are allowed to droop down to the ground.

Cords that

> pull on the camera during the exposure can mess things up. Are your

optics

> stable within the mechanical tube, or do they flop around? Is there

a fan on

> your system somewhere that is vibrating the setup? I've even had

problems

> with the built-in fan on my ST10E in certain orientation. I get

severely

> elongated stars. I had to remove the fan and place some vibration

absorbing

> material between fan and camera body. One way to tell is to turn

off the fan

> and do a short run.

>

> Roland Christen

>

> Roland Christen

>

>

> [Non-text portions of this message have been removed]

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/



----------------------------

#4409 Feb 26 2:22 PM

Did the same thing last night Randy and it worked well for DEC.



John

www.hiddenloft.darkhorizons.org/



-----Original Message-----

From: randy_nulman [mailto:rjnulman@...]

Sent: Tuesday, February 26, 2002 3:16 PM

To: ap-gto@yahoogroups.com

Subject: [ap-gto] Re: 900 GTO tracking problem



Hi Andy,



I believe it's completely possible to *calibrate* and guide at .5x

_IF_ you _accurately_ compensate for backlash during the calibrate

routine...backlash will become much more of an issue at .5x than 1x.



I verify my backlash settings (dec) by doing the following:



During a calibration test, I determine that my initial dec. move

closely matches my RA move (in pixels). Then I look to see if the

movement "back" in dec. puts me within 1 pixel of my intitial

starting point. If so, I begin the guide routine...if not, I adjust

backlash until I get the desired response. (I have found that

different "pointing" postions of the mount will have an affect on the

final results..so I always test the backlash for the _area_ I'm

imaging in)



Randy





--- In ap-gto@y..., "Andy Forsberg" CS-Imaging@p...> wrote:

> Hi John,

>

> It gets worse, I was guiding with my 80mm/900mm AP guide scope

which is evan

> shorter in the region where you are NOT having problems. I'll have

to try

> it with my C11 2800mm and see if I have problems.

> I guess I'm not much help since I have not tried it at the longer

FL. Doug G

> told me to always calibrate at 1x. I'm not sure if he was thinking

in terms

> of focal length when he gave that advice because he knew what I was

using at

> the time.

>

> Wish I could know all the answers. Then I'd have to write a book.

>

> Oh by the way I ordered a FLI CM10 2ME Maxcam. Will use the ST5c

for

> Guiding.

>

> Take care Andy

>

> -----Original Message-----

> From: John Smith [mailto:johnzonie@e...]

> Sent: Tuesday, February 26, 2002 10:23 AM

> To: ap-gto@y...

> Subject: RE: [ap-gto] 900 GTO tracking problem

>

>

> Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am

using the

> guide chip in the ST8. The mount seems to correct after every

exposure.

> I've tried guiding intervals of 4 and 8 seconds. Your 155 has an

FL of 1085

> mm, closer to my 700 mm experience, which was fine. I'm having

trouble at

> the longer FL's.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: Andy Forsberg [mailto:CS-Imaging@p...]

> Sent: Tuesday, February 26, 2002 9:00 AM

> To: ap-gto@y...

> Subject: RE: [ap-gto] 900 GTO tracking problem

>

> John,

>

> What guide rate are you using? How often does the mount correct? I

assume

> you are using the tracking chip in the ST8?

> When at Sunglow I used my ST5c on a separated guide scope and it

worked

> fine. I guess beginners luck. I tracked or corrected at 1x

calibrated at 1x

> and updated each second which may have been too often but it was

working so

> I did not try to fix it.g> It tracked for hours that way. I

remember my

> FWHM was quit large (8) but it held the star spot on. I was able

to hold

> round stars for 10 min unguided so I had good polar alignment.

>

> It sounds like you are doing everything right. What happens when

you shorten

> the tracking interval?

>

> Not much help but maybe trigered the old brain cells.....

> Andy

>

> -----Original Message-----

> From: John Smith [mailto:johnzonie@e...]

> Sent: Tuesday, February 26, 2002 7:16 AM

> To: Ap-Gto

> Subject: [ap-gto] 900 GTO tracking problem

>

>

> Hi,

>

> My 900GTO seemed to track fine when using a scope with a 700 mm FL

(2.65

> arc-sec/pixel). At that FL, the scope load resulted in a single 18-

pound

> counterweight near the top of the shaft. I have recently gone to a

longer

> FL of 1800 mm (1.02 arc-sec./pixel) and am having significant

problems. Now

> the load is balanced by 2 18-pound counterweights approximately 2/3

of the

> way down the shaft. I did expect it to be more difficult but I

haven't been

> successful thus far and am looking for advice.

>

> The DEC axis tracks fine, holding within 0.4 pixels on the tracking

CCD of

> an ST-8E. I have 0 backlash set by the hand controller but have

set it to 1

> for Maxim calibration to get good calibration symmetry in the Y

direction.

> By my calculations, this is around 1.8 arc-sec./pixel. The RA axis

(1.6

> arc-sec./pixel) is giving me fits with as much as 4 pixels peak-to-

peak. I

> would expect any seeing issue to be symmetrical. Here is a typical

image of

> a few minutes of tracking:

>

> www.hiddenloft.darkhorizons.org/guide.jpg

>

> I am using MaximDL v3.05 for CCD control. The camera axes are

parallel to

> RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at

0.5x,

> calibrating and guiding at 0.5x, calibrating and guiding at 1x. I

have

> tried guiding exposures from 4 to 8 seconds, always making sure the

guide

> star is no more than 30k. I have tried making the mount "heavy

east" to the

> tune of 30-40 inch-pounds. I have tried different parts of the sky

with

> similar results. I have checked the RA backlash according to the

AP web

> site. While jiggling the counterweight shaft I wasn't sure I could

detect

> any movement. I rotationally jiggled (does that make sense?) the

brass

> shaft extension and felt a little play and heard a clicking noise

so I

> slightly adjusted the gear engagement. This didn't seem to make any

> improvement.

>

> With this level of tracking performance, a 120 second guided

exposure gives

> stars elongated in the RA direction. Polar alignment is fairly

close,

> certainly within 1 arc-minute. I know the mount is capable of

better

> performance than I am getting and am certain it is cockpit error.

I'm just

> running out of things to try and would welcome any hints or advice.

>

> Thanks,

>

> John

> www.hiddenloft.darkhorizons.org/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/

>

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#4412 Feb 26 2:53 PM

In a message dated 2/26/2002 1:48:49 PM Pacific Standard Time,

Catterall@... writes:



> I have problems with

> DEC tracking, it seems to wander off and take a long time to return to

> the designated tracking pixel



As you know, only RA tracks - at the sidereal rate. The Dec tracking rate is

zero. Therefore I wonder how the mount or image would wander off in the first

place. The only thing I can think of is either the camera is moving slightly

or the optics are shifting. I have seen the effects of camera wires slowly

pulling at the back of the camera and causing declination motion. Fixing the

wires tightly to the mounting plate before running them down to the power

supply/computer port sometimes takes care of these sudden image shifts.

Otherwise, can you give me more information on how the declination axis would

move?



One more thought, several times when I had "The Sky"software hooked up to the

mount, during an image session, a spurious signal was sent to the mount on

this com port from my computer (not the camera guider port). This signal

caused my mount to move in declination by 10 or so arc seconds. This happened

randomly on two different occasions. Physically removing the link from my

laptop to the mount servodrive eliminated this problem. I have tried to

recreate this condition other times, but have not seen it again. To make sure

that no outside signal can interfere, I always now remove the com port wire

from the mount when imaging.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4413 Feb 26 3:01 PM

In a message dated 2/26/2002 1:48:49 PM Pacific Standard Time,

Catterall@... writes:



> I have problems with

> DEC tracking, it seems to wander off



One other thing, don't try to guide with any amount of backlash compensation

in the mount. This will only aggravate the situation. You really do not want

to chase the seeing by allowing the dec axis to go back and forth. It will

become unstable and possibly overshoot. I cannot stress this enough.



Some variables in the dec axis that you can check are the damper knobs

(prevents unwanted movement in windy conditions), too little preload on the

worm (can cause sideways motion of the guide star when the axis tries to

reverse), worm backed off from the worm wheel causing excessive backlash

(will give you poor calibration parameters in Dec). Look at your calibration

parameters. They can tell you a lot about how the mount is responding in the

4 directions.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4414 Feb 26 3:08 PM

In a message dated 2/26/2002 1:52:12 PM Pacific Standard Time,

rjnulman@... writes:



> Roland once pointed out that sometimes seeing/atmospheric movements

> can occur mostly in one direction. Seems odd, but I found it to be

> true...



Another thing happens when you try to image with a long focus instrument

below about 45 degrees altitude. CCD cameras are very sensitive and they will

pick up light far into the IR. At lower altitudes, the stars will spread out

into little spectra aimed up toward the zenith. An unfiltered CCD camera will

pick up this light, and the stars will appear as little ovals instead of

being round. You can very easily mistake this for astigmatism in your optics

or as is usually the case, blame the mount for poor guiding. You can always

tell that its atmospheric dispersion elongating the stars, and not guiding by

taking a fast snapshot of a bright star. Then take one with a green filter.

The filtered one will be round (assuming the optics are ok).



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4415 Feb 26 3:09 PM

In a message dated 2/26/2002 2:25:49 PM Pacific Standard Time,

johnzonie@... writes:



> I believe it's completely possible to *calibrate* and guide at .5x

> _IF_ you _accurately_ compensate for backlash



Also, take twice as long move time if you do calibrate at .5x.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4416 Feb 26 3:14 PM

It's amazing how many variables come into play when guiding.



I still find it hard to believe that seeing errors could only occur

in one direction, but maybe a meteorologist could explain it.

(Sometimes I wonder if my "test" was influenced by cable drag or some

optical movement..as Roland just referred to in a recent reply)



I just know that my guiding performance will vary (sometimes greatly)

from night to night, and I don't think it's mount related..other than

the positional issue I mentioned before.



I would suggest you use the _focus_ FWHM (or 1/2 flux metric) as a

measurement of that night's seeing...look for reasonable stability in

those numbers..and when you see you have a "good" night, then you

know that measurements you perform will be less influenced by seeing

conditions.



Randy

--- In ap-gto@y..., "John Smith" johnzonie@e...> wrote:

> Did the same thing last night Randy and it worked well for DEC.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: randy_nulman [mailto:rjnulman@w...]

> Sent: Tuesday, February 26, 2002 3:16 PM

> To: ap-gto@y...

> Subject: [ap-gto] Re: 900 GTO tracking problem

>

> Hi Andy,

>

> I believe it's completely possible to *calibrate* and guide at .5x

> _IF_ you _accurately_ compensate for backlash during the calibrate

> routine...backlash will become much more of an issue at .5x than 1x.

>

> I verify my backlash settings (dec) by doing the following:

>

> During a calibration test, I determine that my initial dec. move

> closely matches my RA move (in pixels). Then I look to see if the

> movement "back" in dec. puts me within 1 pixel of my intitial

> starting point. If so, I begin the guide routine...if not, I adjust

> backlash until I get the desired response. (I have found that

> different "pointing" postions of the mount will have an affect on

the

> final results..so I always test the backlash for the _area_ I'm

> imaging in)

>

> Randy

>

>

>

> --- In ap-gto@y..., "Andy Forsberg" CS-Imaging@p...> wrote:

> > Hi John,

> >

> > It gets worse, I was guiding with my 80mm/900mm AP guide scope

> which is evan

> > shorter in the region where you are NOT having problems. I'll

have

> to try

> > it with my C11 2800mm and see if I have problems.

> > I guess I'm not much help since I have not tried it at the longer

> FL. Doug G

> > told me to always calibrate at 1x. I'm not sure if he was thinking

> in terms

> > of focal length when he gave that advice because he knew what I

was

> using at

> > the time.

> >

> > Wish I could know all the answers. Then I'd have to write a book.

> >

> > Oh by the way I ordered a FLI CM10 2ME Maxcam. Will use the ST5c

> for

> > Guiding.

> >

> > Take care Andy

> >

> > -----Original Message-----

> > From: John Smith [mailto:johnzonie@e...]

> > Sent: Tuesday, February 26, 2002 10:23 AM

> > To: ap-gto@y...

> > Subject: RE: [ap-gto] 900 GTO tracking problem

> >

> >

> > Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am

> using the

> > guide chip in the ST8. The mount seems to correct after every

> exposure.

> > I've tried guiding intervals of 4 and 8 seconds. Your 155 has an

> FL of 1085

> > mm, closer to my 700 mm experience, which was fine. I'm having

> trouble at

> > the longer FL's.

> >

> > John

> > www.hiddenloft.darkhorizons.org/

> >

> > -----Original Message-----

> > From: Andy Forsberg [mailto:CS-Imaging@p...]

> > Sent: Tuesday, February 26, 2002 9:00 AM

> > To: ap-gto@y...

> > Subject: RE: [ap-gto] 900 GTO tracking problem

> >

> > John,

> >

> > What guide rate are you using? How often does the mount correct? I

> assume

> > you are using the tracking chip in the ST8?

> > When at Sunglow I used my ST5c on a separated guide scope and it

> worked

> > fine. I guess beginners luck. I tracked or corrected at 1x

> calibrated at 1x

> > and updated each second which may have been too often but it was

> working so

> > I did not try to fix it.g> It tracked for hours that way. I

> remember my

> > FWHM was quit large (8) but it held the star spot on. I was able

> to hold

> > round stars for 10 min unguided so I had good polar alignment.

> >

> > It sounds like you are doing everything right. What happens when

> you shorten

> > the tracking interval?

> >

> > Not much help but maybe trigered the old brain cells.....

> > Andy

> >

> > -----Original Message-----

> > From: John Smith [mailto:johnzonie@e...]

> > Sent: Tuesday, February 26, 2002 7:16 AM

> > To: Ap-Gto

> > Subject: [ap-gto] 900 GTO tracking problem

> >

> >

> > Hi,

> >

> > My 900GTO seemed to track fine when using a scope with a 700 mm FL

> (2.65

> > arc-sec/pixel). At that FL, the scope load resulted in a single

18-

> pound

> > counterweight near the top of the shaft. I have recently gone to

a

> longer

> > FL of 1800 mm (1.02 arc-sec./pixel) and am having significant

> problems. Now

> > the load is balanced by 2 18-pound counterweights approximately

2/3

> of the

> > way down the shaft. I did expect it to be more difficult but I

> haven't been

> > successful thus far and am looking for advice.

> >

> > The DEC axis tracks fine, holding within 0.4 pixels on the

tracking

> CCD of

> > an ST-8E. I have 0 backlash set by the hand controller but have

> set it to 1

> > for Maxim calibration to get good calibration symmetry in the Y

> direction.

> > By my calculations, this is around 1.8 arc-sec./pixel. The RA

axis

> (1.6

> > arc-sec./pixel) is giving me fits with as much as 4 pixels peak-

to-

> peak. I

> > would expect any seeing issue to be symmetrical. Here is a

typical

> image of

> > a few minutes of tracking:

> >

> > www.hiddenloft.darkhorizons.org/guide.jpg

> >

> > I am using MaximDL v3.05 for CCD control. The camera axes are

> parallel to

> > RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at

> 0.5x,

> > calibrating and guiding at 0.5x, calibrating and guiding at 1x. I

> have

> > tried guiding exposures from 4 to 8 seconds, always making sure

the

> guide

> > star is no more than 30k. I have tried making the mount "heavy

> east" to the

> > tune of 30-40 inch-pounds. I have tried different parts of the

sky

> with

> > similar results. I have checked the RA backlash according to the

> AP web

> > site. While jiggling the counterweight shaft I wasn't sure I

could

> detect

> > any movement. I rotationally jiggled (does that make sense?) the

> brass

> > shaft extension and felt a little play and heard a clicking noise

> so I

> > slightly adjusted the gear engagement. This didn't seem to make

any

> > improvement.

> >

> > With this level of tracking performance, a 120 second guided

> exposure gives

> > stars elongated in the RA direction. Polar alignment is fairly

> close,

> > certainly within 1 arc-minute. I know the mount is capable of

> better

> > performance than I am getting and am certain it is cockpit error.

> I'm just

> > running out of things to try and would welcome any hints or

advice.

> >

> > Thanks,

> >

> > John

> > www.hiddenloft.darkhorizons.org/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







----------------------------

#4418 Feb 26 3:31 PM

Thanks, Roland:



I recently had a discussion about the use of IR blocking in SCT's.

My understanding was that IR blocking had no benefit with SCT's, but

the other person felt he saw a definite benefit to using it with his.

(obviously talking about clear, lum. exposures here)



Could I construe your comments here to mean that there is a benefit

when at lower altitudes??



Then, if true, what about imaging above 45 deg.? I would prefer to

not use IR blocking in the Lum. due to the increased exposure time.



Thanks,

Randy



--- In ap-gto@y..., chris1011@a... wrote:

> In a message dated 2/26/2002 1:52:12 PM Pacific Standard Time,

> rjnulman@w... writes:

>

>

> > Roland once pointed out that sometimes seeing/atmospheric

movements

> > can occur mostly in one direction. Seems odd, but I found it to

be

> > true...

>

> Another thing happens when you try to image with a long focus

instrument

> below about 45 degrees altitude. CCD cameras are very sensitive and

they will

> pick up light far into the IR. At lower altitudes, the stars will

spread out

> into little spectra aimed up toward the zenith. An unfiltered CCD

camera will

> pick up this light, and the stars will appear as little ovals

instead of

> being round. You can very easily mistake this for astigmatism in

your optics

> or as is usually the case, blame the mount for poor guiding. You

can always

> tell that its atmospheric dispersion elongating the stars, and not

guiding by

> taking a fast snapshot of a bright star. Then take one with a green

filter.

> The filtered one will be round (assuming the optics are ok).

>

> Roland Christen

>

>

> [Non-text portions of this message have been removed]



----------------------------

#4419 Feb 26 4:05 PM

In a message dated 2/26/2002 3:33:57 PM Pacific Standard Time,

rjnulman@... writes:



> Could I construe your comments here to mean that there is a benefit

> when at lower altitudes??



Some kind of filtering will eliminate the oval stars, assuming that your

scope can resolve this small lateral elongation. My 10" F14.6 shows it

easily.



>

> Then, if true, what about imaging above 45 deg.? I would prefer to

> not use IR blocking in the Lum. due to the increased exposure time.

>



Only you can answer that. All I'm doing is making people aware of stuff. If

you don't see the effect, then you have no problems and won't need a filter.

The lateral dispersion effect is real. I can see it even above 45 degrees,

but it gets very small very quickly. Filtering of any kind always makes the

stars round.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4421 Feb 26 8:38 PM

Roland, can you clarify what you mean by this? Are you saying that

we should not be using the backlash compensation built into the

Keypad/controller? Instead, should all the backlash compensation be

done in the software or not at all??



Thanks,



Jerry





> don't try to guide with any amount of backlash compensation

> in the mount. This will only aggravate the situation. You really do

> not wantto chase the seeing by allowing the dec axis to go back and

> forth.



----------------------------

#4422 Feb 27 1:53 AM

I'm sure its software related because as soon as I swap to CCDOPS it

tracks perfectly, even using the same calibration parameters. My

thoughts are that the seeing causes an error and then the corrections

applied are incorrect, perhaps based on the DEC of the object you put in

during calibration and then with guiding? It might be worth trying DEC=0

next time. I've spoken to Doug George at Cyanogen about this, but

perhaps need to go into much more detail to find the problem.



I don't have CCDSoft but am thinking about purchasing because of the

nice sequential imaging capabilities..



Regarding you second email, I agree about DEC backlash compensation

which can vary depending on where in the sky the telescope points, so

always have it set to zero.



Adrian



In message 161.97683eb.29ad6bf0@...>, chris1011@... writes >In a message dated 2/26/2002 1:48:49 PM Pacific Standard Time,

>Catterall@... writes:

>

>

>> I have problems with

>> DEC tracking, it seems to wander off and take a long time to return to

>> the designated tracking pixel

>

>As you know, only RA tracks - at the sidereal rate. The Dec tracking rate is

>zero. Therefore I wonder how the mount or image would wander off in the first

>place. The only thing I can think of is either the camera is moving slightly

>or the optics are shifting. I have seen the effects of camera wires slowly

>pulling at the back of the camera and causing declination motion. Fixing the

>wires tightly to the mounting plate before running them down to the power

>supply/computer port sometimes takes care of these sudden image shifts.

>Otherwise, can you give me more information on how the declination axis would

>move?

>

>One more thought, several times when I had "The Sky"software hooked up to the

>mount, during an image session, a spurious signal was sent to the mount on

>this com port from my computer (not the camera guider port). This signal

>caused my mount to move in declination by 10 or so arc seconds. This happened

>randomly on two different occasions. Physically removing the link from my

>laptop to the mount servodrive eliminated this problem. I have tried to

>recreate this condition other times, but have not seen it again. To make sure

>that no outside signal can interfere, I always now remove the com port wire

>from the mount when imaging.

>

>Roland Christen

>

>

>[Non-text portions of this message have been removed]

>

>

>

>To UNSUBSCRIBE, or for general information on the ap-gto list

>see groups.yahoo.com/group/ap-gto

>

>Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>



--

Adrian Catterall







----------------------------

#4423 Feb 27 5:50 AM

Adrian,

Does not Maxim 3.05 have sequential imaging capability? You can setup a

sequence of images L, R, G, B, and dark and it will number each image in

order and you can walk away and come back later and all is stored on the HD.

Is CCDSoft different?

Andy



-----Original Message-----

From: Adrian Catterall [mailto:Catterall@...]

Sent: Wednesday, February 27, 2002 1:54 AM

To: ap-gto@yahoogroups.com

Subject: Re: [ap-gto] 900 GTO tracking problem



I don't have CCDSoft but am thinking about purchasing because of the

nice sequential imaging capabilities..



----------------------------

#4424 Feb 27 6:58 AM

In a message dated 2/26/2002 8:39:37 PM Pacific Standard Time,

j.zakariasen@... writes:



> Are you saying that

> we should not be using the backlash compensation built into the

> Keypad/controller?



One more time with gusto:



Use the backlash compensation to adjust out the delay time that occurs when

Dec reverses (typically 2 seconds at 1x). However, when you are imaging and

using the autoguider to guide, it is adviseable to reduce the backlash

setting to zero to avoid the dec axis accidentally reversing (say for

instance when the seeing is bad and the guider is trying to chase the

seeing). That is the only time that I recommend removing the compensation.

You can use it on all other occasions if you wish. Personally, I don't ever

use it.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4425 Feb 27 7:13 AM

In a message dated 2/27/2002 3:36:54 AM Pacific Standard Time,

Catterall@... writes:



> My

> thoughts are that the seeing causes an error and then the corrections

> applied are incorrect, perhaps based on the DEC of the object you put in

> during calibration and then with guiding? It might be worth trying DEC=0

> next time



Theoretically, the pixels per second varies from celestial equator to the

poles, thus the need for recalibration in different parts of the sky.

Practically speaking, however, I'm beginning to believe that calibrating only

once near the celestial equator will give parameter values that will work

perfectly everywhere else in the sky (assuming that you reverse the RA motion

in the parameters when you flip the mount). The corollary is not true, you

cannot calibrate near the poles and guide accurately near the celestial

equator.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4426 Feb 27 7:19 AM

In a message dated 2/27/2002 5:53:49 AM Pacific Standard Time,

CS-Imaging@... writes:



> sequence of images L, R, G, B, and dark and it will number each image in

> order and you can walk away and come back later and all is stored on the

> HD.

> Is CCDSoft different



CCDsoft also does this.



Roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4427 Feb 27 7:28 AM

Andy...



Yes it does, just can't use it!! If it wasn't for the guiding issue

MaximDL is a nice friendly package..



I'm stuck with good old CCDOPS!



Adrian





In message NEBBIHDFMPKHPJJPNADJEENGDIAA.CS-Imaging@...>, Andy

Forsberg CS-Imaging@...> writes >Adrian,

>Does not Maxim 3.05 have sequential imaging capability? You can setup a

>sequence of images L, R, G, B, and dark and it will number each image in

>order and you can walk away and come back later and all is stored on the HD.

>Is CCDSoft different?

>Andy

>

>-----Original Message-----

>From: Adrian Catterall [mailto:Catterall@...]

>Sent: Wednesday, February 27, 2002 1:54 AM

>To: ap-gto@yahoogroups.com

>Subject: Re: [ap-gto] 900 GTO tracking problem

>

>I don't have CCDSoft but am thinking about purchasing because of the

>nice sequential imaging capabilities..

>

>

>

>To UNSUBSCRIBE, or for general information on the ap-gto list

>see groups.yahoo.com/group/ap-gto

>

>Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>



--

Adrian Catterall



----------------------------

#4428 Feb 27 7:23 AM

In message 98.2214f004.29ae5193@...>, chris1011@... writes >Theoretically, the pixels per second varies from celestial equator to the

>poles, thus the need for recalibration in different parts of the sky.

>Practically speaking, however, I'm beginning to believe that calibrating only

>once near the celestial equator will give parameter values that will work

>perfectly everywhere else in the sky (assuming that you reverse the RA motion

>in the parameters when you flip the mount). The corollary is not true, you

>cannot calibrate near the poles and guide accurately near the celestial

>equator.

>

>Roland Christen



The feature is built into MaximDL and other software packages, so that

you don't need to re-calibrate when changing objects, but agree with you

that for objects not too far apart in DEC it probably makes little

difference. But I am wondering if there is some bug that effects this.

You mentioned that you were having difficulties too - what were they?



Adrian



--

Adrian Catterall







----------------------------

#4431 Feb 27 2:21 PM

--- In ap-gto@y..., Adrian Catterall Catterall@o...> wrote: > In message 98.2214f004.29ae5193@a...>, chris1011@a... writes

Theoretically, the pixels per second varies from celestial equator to

the poles, thus the need for recalibration in different parts of >

the sky. Practically speaking, however, I'm beginning to believe that

calibrating only

once near the celestial equator will give parameter values that will

work perfectly everywhere else in the sky (assuming that you reverse

the RA motion in the parameters when you flip the mount). The

corollary is not true, you cannot calibrate near the poles and guide

accurately near the celestial

equator. > >

> >Roland Christen

> --



I guess I'm confused...I can easily picture that the calibration in

RA is dependent on the declination - e.g. the number of pixels moved

per second changes when pointing south versus north. But, I cannot

really visualize why the DEC calibration changes as declination

changes. I've assumed that the declination setting in the software

was only for RA compensation. Can someone help me?



Jim McMillan

(eagerly awaiting my AP1200 GTO)



----------------------------

#4433 Feb 27 2:50 PM

In a message dated 2/27/2002 2:23:14 PM Pacific Standard Time,

valueware@... writes:



> But, I cannot

> really visualize why the DEC calibration changes as declination

> changes



Dec does not change.



roland Christen





[Non-text portions of this message have been removed]



----------------------------

#4434 Feb 27 3:19 PM

John,



Not sure if this will help or not, but a few weeks ago I imaged

with my Tak Mewlon 250 at f/12 (3000 mm f.l.) and my AP900 with no

problems. The magic- an AO-7. It does a great job hiding mount

issues and bad parameter settings. I used Maxim DL with

aggressiveness of 10, and calibrated and guided at 1x. The AO-7 sure

is great for me since I don't have a permanent setup and can be more

lazy about mount setup than otherwise. This is very good since I

have to spend time setting up and polar aligning every session.



Good luck,

Chris Durand

--- In ap-gto@y..., "John Smith" johnzonie@e...> wrote:

> Did the same thing last night Randy and it worked well for DEC.

>

> John

> www.hiddenloft.darkhorizons.org/

>

> -----Original Message-----

> From: randy_nulman [mailto:rjnulman@w...]

> Sent: Tuesday, February 26, 2002 3:16 PM

> To: ap-gto@y...

> Subject: [ap-gto] Re: 900 GTO tracking problem

>

> Hi Andy,

>

> I believe it's completely possible to *calibrate* and guide at .5x

> _IF_ you _accurately_ compensate for backlash during the calibrate

> routine...backlash will become much more of an issue at .5x than 1x.

>

> I verify my backlash settings (dec) by doing the following:

>

> During a calibration test, I determine that my initial dec. move

> closely matches my RA move (in pixels). Then I look to see if the

> movement "back" in dec. puts me within 1 pixel of my intitial

> starting point. If so, I begin the guide routine...if not, I adjust

> backlash until I get the desired response. (I have found that

> different "pointing" postions of the mount will have an affect on

the

> final results..so I always test the backlash for the _area_ I'm

> imaging in)

>

> Randy

>

>

>

> --- In ap-gto@y..., "Andy Forsberg" CS-Imaging@p...> wrote:

> > Hi John,

> >

> > It gets worse, I was guiding with my 80mm/900mm AP guide scope

> which is evan

> > shorter in the region where you are NOT having problems. I'll

have

> to try

> > it with my C11 2800mm and see if I have problems.

> > I guess I'm not much help since I have not tried it at the longer

> FL. Doug G

> > told me to always calibrate at 1x. I'm not sure if he was thinking

> in terms

> > of focal length when he gave that advice because he knew what I

was

> using at

> > the time.

> >

> > Wish I could know all the answers. Then I'd have to write a book.

> >

> > Oh by the way I ordered a FLI CM10 2ME Maxcam. Will use the ST5c

> for

> > Guiding.

> >

> > Take care Andy

> >

> > -----Original Message-----

> > From: John Smith [mailto:johnzonie@e...]

> > Sent: Tuesday, February 26, 2002 10:23 AM

> > To: ap-gto@y...

> > Subject: RE: [ap-gto] 900 GTO tracking problem

> >

> >

> > Thanks, Andy. I have been guiding at 1x and 0/5x and yes, I am

> using the

> > guide chip in the ST8. The mount seems to correct after every

> exposure.

> > I've tried guiding intervals of 4 and 8 seconds. Your 155 has an

> FL of 1085

> > mm, closer to my 700 mm experience, which was fine. I'm having

> trouble at

> > the longer FL's.

> >

> > John

> > www.hiddenloft.darkhorizons.org/

> >

> > -----Original Message-----

> > From: Andy Forsberg [mailto:CS-Imaging@p...]

> > Sent: Tuesday, February 26, 2002 9:00 AM

> > To: ap-gto@y...

> > Subject: RE: [ap-gto] 900 GTO tracking problem

> >

> > John,

> >

> > What guide rate are you using? How often does the mount correct? I

> assume

> > you are using the tracking chip in the ST8?

> > When at Sunglow I used my ST5c on a separated guide scope and it

> worked

> > fine. I guess beginners luck. I tracked or corrected at 1x

> calibrated at 1x

> > and updated each second which may have been too often but it was

> working so

> > I did not try to fix it.g> It tracked for hours that way. I

> remember my

> > FWHM was quit large (8) but it held the star spot on. I was able

> to hold

> > round stars for 10 min unguided so I had good polar alignment.

> >

> > It sounds like you are doing everything right. What happens when

> you shorten

> > the tracking interval?

> >

> > Not much help but maybe trigered the old brain cells.....

> > Andy

> >

> > -----Original Message-----

> > From: John Smith [mailto:johnzonie@e...]

> > Sent: Tuesday, February 26, 2002 7:16 AM

> > To: Ap-Gto

> > Subject: [ap-gto] 900 GTO tracking problem

> >

> >

> > Hi,

> >

> > My 900GTO seemed to track fine when using a scope with a 700 mm FL

> (2.65

> > arc-sec/pixel). At that FL, the scope load resulted in a single

18-

> pound

> > counterweight near the top of the shaft. I have recently gone to

a

> longer

> > FL of 1800 mm (1.02 arc-sec./pixel) and am having significant

> problems. Now

> > the load is balanced by 2 18-pound counterweights approximately

2/3

> of the

> > way down the shaft. I did expect it to be more difficult but I

> haven't been

> > successful thus far and am looking for advice.

> >

> > The DEC axis tracks fine, holding within 0.4 pixels on the

tracking

> CCD of

> > an ST-8E. I have 0 backlash set by the hand controller but have

> set it to 1

> > for Maxim calibration to get good calibration symmetry in the Y

> direction.

> > By my calculations, this is around 1.8 arc-sec./pixel. The RA

axis

> (1.6

> > arc-sec./pixel) is giving me fits with as much as 4 pixels peak-

to-

> peak. I

> > would expect any seeing issue to be symmetrical. Here is a

typical

> image of

> > a few minutes of tracking:

> >

> > www.hiddenloft.darkhorizons.org/guide.jpg

> >

> > I am using MaximDL v3.05 for CCD control. The camera axes are

> parallel to

> > RA/DEC within 0.5(. I have tried calibrating at 1x and guiding at

> 0.5x,

> > calibrating and guiding at 0.5x, calibrating and guiding at 1x. I

> have

> > tried guiding exposures from 4 to 8 seconds, always making sure

the

> guide

> > star is no more than 30k. I have tried making the mount "heavy

> east" to the

> > tune of 30-40 inch-pounds. I have tried different parts of the

sky

> with

> > similar results. I have checked the RA backlash according to the

> AP web

> > site. While jiggling the counterweight shaft I wasn't sure I

could

> detect

> > any movement. I rotationally jiggled (does that make sense?) the

> brass

> > shaft extension and felt a little play and heard a clicking noise

> so I

> > slightly adjusted the gear engagement. This didn't seem to make

any

> > improvement.

> >

> > With this level of tracking performance, a 120 second guided

> exposure gives

> > stars elongated in the RA direction. Polar alignment is fairly

> close,

> > certainly within 1 arc-minute. I know the mount is capable of

> better

> > performance than I am getting and am certain it is cockpit error.

> I'm just

> > running out of things to try and would welcome any hints or

advice.

> >

> > Thanks,

> >

> > John

> > www.hiddenloft.darkhorizons.org/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> >

> >

> >

> >

> > To UNSUBSCRIBE, or for general information on the ap-gto list

> > see groups.yahoo.com/group/ap-gto

> >

> > Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/







Contact Us
This Site's Privacy Policy
Google's privacy policies

S
e
n
i
o
r
T
u
b
e
.
o
r
g