Re: [ap-gto] 900 GTO and Tpoint


Nov 8, 2002

 


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

#6013 Nov 8, 2002

I have playing around with Tpoint to polar align my mount. I used the

GTO Quick Star Drift Method of Polar Alignment on page 46 of my GTO

keypad controller manual.



My Tpoint numbers for polar alignment came up as follows:



19 arcseconds to low in the Altitude from the pole



52 arcseconds east from the pole



I have a permanent observatory.



Questions:



1. These polar numbers really are terrible.... correct?

2. Are there any guidelines on how to turn the knobs on the GTO mount

to fix the errors in arcseconds?



thanks



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

#6015 Nov 8, 2002

At 09:17 PM 11/8/2002 -0500, you wrote: >I have playing around with Tpoint to polar align my mount. I used the

>GTO Quick Star Drift Method of Polar Alignment on page 46 of my GTO

>keypad controller manual.

>

>My Tpoint numbers for polar alignment came up as follows:

>

>19 arcseconds to low in the Altitude from the pole

>

>52 arcseconds east from the pole

>

>I have a permanent observatory.

>

>Questions:

>

>1. These polar numbers really are terrible.... correct?

>2. Are there any guidelines on how to turn the knobs on the GTO mount

>to fix the errors in arcseconds?

>

>thanks



No, your numbers are pretty good, getting anything under one minute of arc

is difficult. I am assuming that you did a whole sky mapping run, you are

not using a SCT with mirror shift, and you sampled as they suggest. You

will chase those numbers around if you go and start turning knobs. Also,

be advised that the number of terms that you add to the model will change

polar alignment information.



Mike J. Shade: mshade@...

Sonoita Hills Observatory, Sonoita Arizona



See work done at the observatory: c3po.cochise.cc.az.us/astro

under the "photographs and images" panel on the left of the screen.



"I like the dark, it's cheap." E. B. Scrooge



International Dark sky Association www.darksky.org "I'm a member, are you?"



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

#6016 Nov 9, 2002

Thanks for your comments Mike



Yep I used an AP 155 to do the mapping and on both sides of the

meridian.



And yep, I learned that changing the terms, changes the polar numbers.



Joe







On Saturday, November 9, 2002, at 01:57 AM, Mike J. Shade wrote:



> At 09:17 PM 11/8/2002 -0500, you wrote:

>> I have playing around with Tpoint to polar align my mount. I used the

>> GTO Quick Star Drift Method of Polar Alignment on page 46 of my GTO

>> keypad controller manual.

>>

>> My Tpoint numbers for polar alignment came up as follows:

>>

>> 19 arcseconds to low in the Altitude from the pole

>>

>> 52 arcseconds east from the pole

>>

>> I have a permanent observatory.

>>

>> Questions:

>>

>> 1. These polar numbers really are terrible.... correct?

>> 2. Are there any guidelines on how to turn the knobs on the GTO mount

>> to fix the errors in arcseconds?

>>

>> thanks

>

> No, your numbers are pretty good, getting anything under one minute of

> arc

> is difficult. I am assuming that you did a whole sky mapping run, you

> are

> not using a SCT with mirror shift, and you sampled as they suggest.

> You

> will chase those numbers around if you go and start turning knobs.

> Also,

> be advised that the number of terms that you add to the model will

> change

> polar alignment information.

>

> Mike J. Shade: mshade@...

> Sonoita Hills Observatory, Sonoita Arizona

>

> See work done at the observatory: c3po.cochise.cc.az.us/astro

> under the "photographs and images" panel on the left of the screen.

>

> "I like the dark, it's cheap." E. B. Scrooge

>

> International Dark sky Association www.darksky.org "I'm a member, are

> you?"

>

>

>

>

> 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/

>

>



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

#6019 Nov 11, 2002

In a message dated 11/8/2002 8:17:09 PM Central Standard Time,

jmarietta@... writes:



> I have playing around with Tpoint to polar align my mount. I used the

> GTO Quick Star Drift Method of Polar Alignment on page 46 of my GTO

> keypad controller manual.

>

> My Tpoint numbers for polar alignment came up as follows:

>

> 19 arcseconds to low in the Altitude from the pole

>

> 52 arcseconds east from the pole

>



I guess it depends what you want T-Point to do for you. One of the main uses

for this program is in automated observatories where you need the land

objects dead center on your chip anywhere in the sky. The program does this

by compensating for any number of irregularities including non-perfect polar

alignment, non-orthogonality, atmospheric refraction, mirror flop in the case

of Cassegrains, equatorial mount errors of all kinds and a host of other

things. The program does not require you to be perfectly polar aligned. When

Walter set up the 1200 mount at the ISSAT facility, he only roughly aligned

the mount to the pole using the pole scope. Then he expected the technicians

to further refine the polar alignment uaing T-Point because he was off by

several arc minutes. To his surprise, the technicians did not change the

alignment, saying it would not matter to be any closer. In spite of the polar

error, they managed to point the C14 to within 7.1 arc seconds anywhere in

the sky.



If you want to align your mount for minimum drift, then the best way to do

this is with the drift method, either the classical approach, or by

monitoring the drift using your CCD camera. I have gone over this several

times now in this group, so perhaps it is time to put the procedure on our

web site. Perhaps someone else can go through the archives and dig up for Joe

what myself and others have written about drift alignment. Meanwhile, I'll

work up a text also. By the way, drift alignment with a CCD is deadly

accurate in eliminating drift. I have managed to do 10 minute unguided shots

at 3700mm focal length. I used CCDOPS Track&Accumulate to monitor the

magnitude and direction of the drift, and slowly reduce it by turning the Alt

and Az adjusters. I then used T&A in relay mode to record my periodic error

to the PEM memory to bring the PE down from 3 arc sec to under 1 arc sec. If

time permits, I will post my track logs in the next couple of days.



Roland Christen





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







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

#6060 Nov 12, 2002

Hi Roland



I surfed the web and found the following link:



www.hiddenloft.darkhorizons.org/notes/palign.txt



This is a text file of the procedure you did at Trent's observatory and

I think it answers my question on CCD drift for polar alignment.



My goal, to be able to take 5 to 10 minute unguided exposures with my

ST 2000 and 900 GTO/155 AP.



I understand your text file article completely including the PEM

procedure. However in the message below you state the following:

> " I then used T&A in relay mode to record my periodic error

> to the PEM memory to bring the PE down from 3 arc sec to under 1 arc

> sec. If

> time permits, I will post my track logs in the next couple of days."



By relay mode, do you mean you use the autoguider mode in CCDOPS to

track a star for 7 minutes and record the PEM?





Thanks

Joe







On Monday, November 11, 2002, at 09:03 AM, chris1011@... wrote:



> In a message dated 11/8/2002 8:17:09 PM Central Standard Time,

> jmarietta@... writes:

>

>

>> I have playing around with Tpoint to polar align my mount. I used the

>> GTO Quick Star Drift Method of Polar Alignment on page 46 of my GTO

>> keypad controller manual.

>>

>> My Tpoint numbers for polar alignment came up as follows:

>>

>> 19 arcseconds to low in the Altitude from the pole

>>

>> 52 arcseconds east from the pole

>>

>

> I guess it depends what you want T-Point to do for you. One of the

> main uses

> for this program is in automated observatories where you need the land

> objects dead center on your chip anywhere in the sky. The program does

> this

> by compensating for any number of irregularities including non-perfect

> polar

> alignment, non-orthogonality, atmospheric refraction, mirror flop in

> the case

> of Cassegrains, equatorial mount errors of all kinds and a host of

> other

> things. The program does not require you to be perfectly polar

> aligned. When

> Walter set up the 1200 mount at the ISSAT facility, he only roughly

> aligned

> the mount to the pole using the pole scope. Then he expected the

> technicians

> to further refine the polar alignment uaing T-Point because he was off

> by

> several arc minutes. To his surprise, the technicians did not change

> the

> alignment, saying it would not matter to be any closer. In spite of

> the polar

> error, they managed to point the C14 to within 7.1 arc seconds

> anywhere in

> the sky.

>

> If you want to align your mount for minimum drift, then the best way

> to do

> this is with the drift method, either the classical approach, or by

> monitoring the drift using your CCD camera. I have gone over this

> several

> times now in this group, so perhaps it is time to put the procedure on

> our

> web site. Perhaps someone else can go through the archives and dig up

> for Joe

> what myself and others have written about drift alignment. Meanwhile,

> I'll

> work up a text also. By the way, drift alignment with a CCD is deadly

> accurate in eliminating drift. I have managed to do 10 minute unguided

> shots

> at 3700mm focal length. I used CCDOPS Track&Accumulate to monitor the

> magnitude and direction of the drift, and slowly reduce it by turning

> the Alt

> and Az adjusters. I then used T&A in relay mode to record my periodic

> error

> to the PEM memory to bring the PE down from 3 arc sec to under 1 arc

> sec. If

> time permits, I will post my track logs in the next couple of days.

>

> 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/

>

>



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

#6062 Nov 12, 2002

In a message dated 11/12/2002 9:44:32 AM Central Standard Time,

jmarietta@... writes:



> By relay mode, do you mean you use the autoguider mode in CCDOPS to

> track a star for 7 minutes and record the PEM?

>



You can use the autoguider mode, but you won't really be seeing what is

happening. If you use T&A in relay mode (actually use the "both" mode), you

will get a nice graph of the moment to moment error that is being recorded to

your servo memory. Why is this important? Because if you see an anomolous

spike, perhaps caused by a random atmospheric instbility, you might want to

reject this run and try again for a clean run. The T&A graph will show you

exactly what you have recorded, and when you go to playback mode, you will

see similar tracking in subsequent unguided exposures.



I set up my T&A using either the guide chip for very fast downloads, or I go

into 1/4 frame with 2x2 binning in the main chip. Fast downloads are

important because you want to store your corrections the moment they happen,

not 8 seconds later. Choose intervals of 1-2 seconds for your corrections.

Longer intervals will put too much delay into your data.



Roland Christen





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







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

#6077 Nov 13, 2002

Hi

I bought Tpoint to corret the orthogolality error of my C14 with my 900GTO,

are you sure that Tpoint also correct miror flop, it don't seem to be ok in

my case...

I'm also interested in by the method of minimum drift with CCDOPS

Track&Accumulate, could you explain me again the method....

Bye

Vincent from France

> by compensating for any number of irregularities including non-perfect

polar > alignment, non-orthogonality, atmospheric refraction, mirror flop in the

case > of Cassegrains, equatorial mount errors of all kinds and a host of other

> things. The program does not require you to be perfectly polar aligned.

When > Walter set up the 1200 mount at the ISSAT facility, he only roughly

aligned > the mount to the pole using the pole scope. Then he expected the

technicians > to further refine the polar alignment uaing T-Point because he was off by

> several arc minutes. To his surprise, the technicians did not change the

> alignment, saying it would not matter to be any closer. In spite of the

polar > error, they managed to point the C14 to within 7.1 arc seconds anywhere in

> the sky.

>

> If you want to align your mount for minimum drift, then the best way to do

> this is with the drift method, either the classical approach, or by

> monitoring the drift using your CCD camera. I have gone over this several

> times now in this group, so perhaps it is time to put the procedure on our

> web site. Perhaps someone else can go through the archives and dig up for

Joe > what myself and others have written about drift alignment. Meanwhile, I'll

> work up a text also. By the way, drift alignment with a CCD is deadly

> accurate in eliminating drift. I have managed to do 10 minute unguided

shots > at 3700mm focal length. I



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