VintageBigBlue.org

 

Re: PE improvement


Apr 17, 2006

 


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

#29494 Apr 17, 2006

I have just uploaded the latest results from my on going battle with

improving the tracking of my G11 (please see PEC saga.doc in the files

section). Things are much better than when I started, but still not

quite good enough, i.e. I still get trails on 20/30 sec exposures with

an autoguider running. (NB I know I am pushing the limits since I'm

imaging at 0.66"/pixel)



It seems I have eliminated the largest source of error. The

76sec 'sorta' periodic peaks that are due to ball bearing compression

in the worm bearing blocks. Diggin thru archives here and on the net

in general this has been solved before.



My fix was to use a Dremel tool to enlarge the bearing holes with a

0.625" disk (lucky me, the bearing are 0.625" OD). The disk consists

of a cylindrical piece of rough sand paper over a solid rubber

cylinder. The top 80% of the depth takes less than 2 seconds at

2500RPM, but the disk tappers slightly so it doesnt grind out the

bottom. So the last 20% near the bottom was done by turning the disk

by hand for 5-10 min.



I replaced the bearings with stock McMaster-Carr ABEC5 bearings (SR4ZZ

I think) (5$ each). The original bearing had to be knock out with 3/8"

diameter bolt and hammer, they were that tight! To get the bearing out

of the far block (wrt the motor) I had to drill thru the back side of

the block with a 3/8" bit.



Now my biggest concern are the recurrent jumps in the tracking that

seem quite periodic. Does anyone know what these are from? What

possible solutions I might try? Or is it hopeless and this is what

I've got. Is anybody else willing to post track logs or PEMpro results

so that I might know what is achievable?



One thing I might try next is to put the helical coupler back on, also

I think I might swap the worms again to see if the characteristic

jumps change.



Thanks for listening,

Eric



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

#29495 Apr 17, 2006

If you're still getting jumps and stuff like that, perhaps you should order

new worm, blocks and bearings directly from Losmandy. It certainly isn't

normal to see that kind of performance. My new G11 is giving me .8 arc

seconds either side of center with PEC OFF. I get no funny jumps or peaks.

It would cost $15 for the bearings, 30 for the blocks and 50 for a new high

precision worm. I hear you altering the coupling, bearings, etc. Based on

the performance of my mount I know it is capable of extremely accurate

tracking in "stock" condition. If you're having problems from your

configuration I'd recommend swapping out the entire worm assembly (and

ordering stock couplings). Certainly call Losmandy for an expert

recomendation. BTW, if your spkes are repeating every 4 minutes it must be

in the worm. If it's happening more often it's probably the coupling.



Tom P.



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

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

On Behalf Of ericwbenson

Sent: Monday, April 17, 2006 1:43 PM

To: Losmandy_users@yahoogroups.com

Subject: [Losmandy_users] PE improvement





I have just uploaded the latest results from my on going battle with

improving the tracking of my G11 (please see PEC saga.doc in the files

section). Things are much better than when I started, but still not

quite good enough, i.e. I still get trails on 20/30 sec exposures with

an autoguider running. (NB I know I am pushing the limits since I'm

imaging at 0.66"/pixel)



It seems I have eliminated the largest source of error. The

76sec 'sorta' periodic peaks that are due to ball bearing compression

in the worm bearing blocks. Diggin thru archives here and on the net

in general this has been solved before.



My fix was to use a Dremel tool to enlarge the bearing holes with a

0.625" disk (lucky me, the bearing are 0.625" OD). The disk consists

of a cylindrical piece of rough sand paper over a solid rubber

cylinder. The top 80% of the depth takes less than 2 seconds at

2500RPM, but the disk tappers slightly so it doesnt grind out the

bottom. So the last 20% near the bottom was done by turning the disk

by hand for 5-10 min.



I replaced the bearings with stock McMaster-Carr ABEC5 bearings (SR4ZZ

I think) (5$ each). The original bearing had to be knock out with 3/8"

diameter bolt and hammer, they were that tight! To get the bearing out

of the far block (wrt the motor) I had to drill thru the back side of

the block with a 3/8" bit.



Now my biggest concern are the recurrent jumps in the tracking that

seem quite periodic. Does anyone know what these are from? What

possible solutions I might try? Or is it hopeless and this is what

I've got. Is anybody else willing to post track logs or PEMpro results

so that I might know what is achievable?



One thing I might try next is to put the helical coupler back on, also

I think I might swap the worms again to see if the characteristic

jumps change.



Thanks for listening,

Eric











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







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

#29496 Apr 17, 2006

Eric, there are a few old PE charts in the files section:



groups.yahoo.com/group/Losmandy_users/files/G-11%20PE%

20test.jpg



groups.yahoo.com/group/Losmandy_users/files/g11-pe.jpg



The second one is mine, and I actually got it to go a bit lower,

just under +/-2 arcseconds with better worm alignment and new

grease. My PE used to be about +/-4" with the original RA worm. I

replaced it with high-precision one when these came out, and then

swapped RA and DEC to get the performance you see in the chart.



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "ericwbenson" ebenson@...>

wrote: >

> I have just uploaded the latest results from my on going battle

with > improving the tracking of my G11 (please see PEC saga.doc in the

files > section). Things are much better than when I started, but still

not > quite good enough, i.e. I still get trails on 20/30 sec exposures

with > an autoguider running. (NB I know I am pushing the limits since

I'm > imaging at 0.66"/pixel)

>

> It seems I have eliminated the largest source of error. The

> 76sec 'sorta' periodic peaks that are due to ball bearing

compression > in the worm bearing blocks. Diggin thru archives here and on the

net > in general this has been solved before.

>

> My fix was to use a Dremel tool to enlarge the bearing holes with

a > 0.625" disk (lucky me, the bearing are 0.625" OD). The disk

consists > of a cylindrical piece of rough sand paper over a solid rubber

> cylinder. The top 80% of the depth takes less than 2 seconds at

> 2500RPM, but the disk tappers slightly so it doesnt grind out the

> bottom. So the last 20% near the bottom was done by turning the

disk > by hand for 5-10 min.

>

> I replaced the bearings with stock McMaster-Carr ABEC5 bearings

(SR4ZZ > I think) (5$ each). The original bearing had to be knock out with

3/8" > diameter bolt and hammer, they were that tight! To get the bearing

out > of the far block (wrt the motor) I had to drill thru the back side

of > the block with a 3/8" bit.

>

> Now my biggest concern are the recurrent jumps in the tracking

that > seem quite periodic. Does anyone know what these are from? What

> possible solutions I might try? Or is it hopeless and this is what

> I've got. Is anybody else willing to post track logs or PEMpro

results > so that I might know what is achievable?

>

> One thing I might try next is to put the helical coupler back on,

also > I think I might swap the worms again to see if the characteristic

> jumps change.

>

> Thanks for listening,

> Eric

>



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

#29499 Apr 18, 2006

Swapped the worms and motor/gearboxes last night, no difference in

tracked image quality, PE about the same (PEMpro reports ~1.3"), my

worm alignment was worse than before (did it in twilight/darkness in

the backyard in a hurry).



I've been thinking of sending the worms back (or buying new ones), I

dont think the couplers are a problem (anyways I only moded one of

the Oldham's and it's on the DEC axis), I'm fairly certain I have

improved the worm bearings... But I am also wondering if the problem

is a rough RA gear. Hard to diagnose (let's see I could guide on star

A then slew to a star B 4min back in RA, repeat for star C, not sure

it's feasible).



Has anyone swapped the RA and DEC gears (or assemblies if they are

the same dimensions)?



Has anyone noticed a difference in "roughness" (I use this term to

describe the fast jumps, slope > 1"/sec, that cant be guided out)

when changing the clutch pressure. This I can try tonight.



Just a thought: a 1"/sec slope, random in direction, produces zero

PE, but it seems as damaging to an autoguided image as a perfectly

sinusoidal 120" p-p PE. This is what I am fighting, the rolling bumps

the guider can handle.



OTOH Looking at Paul K.'s track graph, I think I have nearly the same

behaviour in my most recent attempts. He seems happy with his mount

but my autoguided 10sec images still shows severly oblong stars

grrrrrr. Am I asking too much of this mount at 0.66"/pixel?



If anyone has a raw track log with autoguiding turned off on both

axes I would really appreciate it if you sent it to me. I am

analyzing the "instanteneous" error distribution (sorta like the

histogram in PEMpro) and I would like other logs to compare to.



Appreciate your coments,

Eric B.



--- In Losmandy_users@yahoogroups.com, "Thomas Picciani"

tpicciani@...> wrote: >

> If you're still getting jumps and stuff like that, perhaps you

should order > new worm, blocks and bearings directly from Losmandy. It certainly

isn't > normal to see that kind of performance. My new G11 is giving me .8

arc > seconds either side of center with PEC OFF. I get no funny jumps or

peaks. > It would cost $15 for the bearings, 30 for the blocks and 50 for a

new high > precision worm. I hear you altering the coupling, bearings, etc.

Based on > the performance of my mount I know it is capable of extremely

accurate > tracking in "stock" condition. If you're having problems from your

> configuration I'd recommend swapping out the entire worm assembly

(and > ordering stock couplings). Certainly call Losmandy for an expert

> recomendation. BTW, if your spkes are repeating every 4 minutes it

must be > in the worm. If it's happening more often it's probably the

coupling. >

> Tom P.

>

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

> From: Losmandy_users@yahoogroups.com

[mailto:Losmandy_users@yahoogroups.com] > On Behalf Of ericwbenson

> Sent: Monday, April 17, 2006 1:43 PM

> To: Losmandy_users@yahoogroups.com

> Subject: [Losmandy_users] PE improvement

>

>

> I have just uploaded the latest results from my on going battle

with > improving the tracking of my G11 (please see PEC saga.doc in the

files > section). Things are much better than when I started, but still not

> quite good enough, i.e. I still get trails on 20/30 sec exposures

with > an autoguider running. (NB I know I am pushing the limits since I'm

> imaging at 0.66"/pixel)

>

> It seems I have eliminated the largest source of error. The

> 76sec 'sorta' periodic peaks that are due to ball bearing

compression > in the worm bearing blocks. Diggin thru archives here and on the

net > in general this has been solved before.

>

> My fix was to use a Dremel tool to enlarge the bearing holes with a

> 0.625" disk (lucky me, the bearing are 0.625" OD). The disk

consists > of a cylindrical piece of rough sand paper over a solid rubber

> cylinder. The top 80% of the depth takes less than 2 seconds at

> 2500RPM, but the disk tappers slightly so it doesnt grind out the

> bottom. So the last 20% near the bottom was done by turning the

disk > by hand for 5-10 min.

>

> I replaced the bearings with stock McMaster-Carr ABEC5 bearings

(SR4ZZ > I think) (5$ each). The original bearing had to be knock out with

3/8" > diameter bolt and hammer, they were that tight! To get the bearing

out > of the far block (wrt the motor) I had to drill thru the back side

of > the block with a 3/8" bit.

>

> Now my biggest concern are the recurrent jumps in the tracking that

> seem quite periodic. Does anyone know what these are from? What

> possible solutions I might try? Or is it hopeless and this is what

> I've got. Is anybody else willing to post track logs or PEMpro

results > so that I might know what is achievable?

>

> One thing I might try next is to put the helical coupler back on,

also > I think I might swap the worms again to see if the characteristic

> jumps change.

>

> Thanks for listening,

> Eric

>

>

>

>

>

> _____

>

> YAHOO! GROUPS LINKS

>

>

> .

> *. Visit your group "Losmandy_users

> groups.yahoo.com/group/Losmandy_users> " on the web.

>

>

> *. To unsubscribe from this group, send an email to:

> Losmandy_users-unsubscribe@yahoogroups.com

> mailto:Losmandy_users-unsubscribe@yahoogroups.com?

subject=Unsubscribe> >

>

> *. Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service > docs.yahoo.com/info/terms/> .

>

>

> _____

>

>

>

>

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

>







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

#29501 Apr 18, 2006

I'm sorry I meant 1.3" RMS, +3.1/-3" PE. The data I gathered the

night before was essentially the same as last nights run. The PEMpro

screen shots are in the files section (see PEC saga.doc).



I have a C11 with Taurus Tracker III oag, ST7EI main camera, SX716usb

guider. When gathering the tracking data I use the ST7EI straight

through since it's easier to setup, represents the best case

sceanario etc. The guider exposures have typically been 0.5 to 1 sec

long, the guide rate is as fast as maxim can go, which seems to be

about every 2 sec even for very short exposures.



The mount was bought brand new in Jan 06, so up to now I figured the

bearings should be clean and properly greased!!! I took the RA axis

apart this morning, I saw some dirt on the nylon (?) clutch pad. When

turning the RA axis, I could imaging hearing a grinding/crackling

noise, or is it just a swoosh, not sure, dont know what it's supposed

to sound like.



I just polished the RA thrust bearing washers, they are certainly

shinier than before, maybe that will help...



I'm glad to know that 0.5"/pixel is possible. It's funny when I wrote

the MaxIm AO7 driver years ago we used to kid around how it made so

many bad mounts look good, but didnt do much adaptive optic "seeing

fixing". Now that I'm blessed with a mount that is not doing what I

want, I feel what many people must have felt before when eyeing the

AO7 unit. Too bad my ST7 only has one chip.



Eric B.

--- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@...> wrote:

>

> Eric,

>

> 1.3" PE is very good, unless there are random errors or the

tracking

> rate is off. Can you please post a Pempro chart showing the data

> you've gathered?

>

> It's easy enough to check if the gear is the problem: simply slew

to

> another part of the sky in RA, then move the telescope back by hand

> to to the starting point: you'll now be using a different part of

> the gear.

>

> There are four other bearings in the axis assembly that may be

> stuck, dirty, or just need new grease. It may be worth a check if

> you see random errors.

>

> I successfully and consistenly took 20 minute exposures at

> 0.5 "/pixel with the mount performance as shown in that chart, so I

> am fairly sure it's doable ;-)

>

> Oblong stars could also be the result of flexure or mirror flop.

> What telescope and guiding setup are you using? How frequent are

> your guider exposures? What guide rate are you using?

>

> Regards,

>

> -Paul

>

>

> --- In Losmandy_users@yahoogroups.com, "ericwbenson" ebenson@>

> wrote:

> >

> > Swapped the worms and motor/gearboxes last night, no difference

in

> > tracked image quality, PE about the same (PEMpro reports ~1.3"),

> my

> > worm alignment was worse than before (did it in twilight/darkness

> in

> > the backyard in a hurry).

> >

> > I've been thinking of sending the worms back (or buying new

ones),

> I

> > dont think the couplers are a problem (anyways I only moded one

of

> > the Oldham's and it's on the DEC axis), I'm fairly certain I have

> > improved the worm bearings... But I am also wondering if the

> problem

> > is a rough RA gear. Hard to diagnose (let's see I could guide on

> star

> > A then slew to a star B 4min back in RA, repeat for star C, not

> sure

> > it's feasible).

> >

> > Has anyone swapped the RA and DEC gears (or assemblies if they

are

> > the same dimensions)?

> >

> > Has anyone noticed a difference in "roughness" (I use this term

to

> > describe the fast jumps, slope > 1"/sec, that cant be guided out)

> > when changing the clutch pressure. This I can try tonight.

> >

> > Just a thought: a 1"/sec slope, random in direction, produces

zero

> > PE, but it seems as damaging to an autoguided image as a

perfectly

> > sinusoidal 120" p-p PE. This is what I am fighting, the rolling

> bumps

> > the guider can handle.

> >

> > OTOH Looking at Paul K.'s track graph, I think I have nearly the

> same

> > behaviour in my most recent attempts. He seems happy with his

> mount

> > but my autoguided 10sec images still shows severly oblong stars

> > grrrrrr. Am I asking too much of this mount at 0.66"/pixel?

> >

> > If anyone has a raw track log with autoguiding turned off on both

> > axes I would really appreciate it if you sent it to me. I am

> > analyzing the "instanteneous" error distribution (sorta like the

> > histogram in PEMpro) and I would like other logs to compare to.

> >

> > Appreciate your coments,

> > Eric B.

> >

> > --- In Losmandy_users@yahoogroups.com, "Thomas Picciani"

> > tpicciani@> wrote:

> > >

> > > If you're still getting jumps and stuff like that, perhaps you

> > should order

> > > new worm, blocks and bearings directly from Losmandy. It

> certainly

> > isn't

> > > normal to see that kind of performance. My new G11 is giving

> me .8

> > arc

> > > seconds either side of center with PEC OFF. I get no funny

jumps

> or

> > peaks.

> > > It would cost $15 for the bearings, 30 for the blocks and 50

for

> a

> > new high

> > > precision worm. I hear you altering the coupling, bearings,

etc.

> > Based on

> > > the performance of my mount I know it is capable of extremely

> > accurate

> > > tracking in "stock" condition. If you're having problems from

> your

> > > configuration I'd recommend swapping out the entire worm

> assembly

> > (and

> > > ordering stock couplings). Certainly call Losmandy for an expert

> > > recomendation. BTW, if your spkes are repeating every 4 minutes

> it

> > must be

> > > in the worm. If it's happening more often it's probably the

> > coupling.

> > >

> > > Tom P.

> > >

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

> > > From: Losmandy_users@yahoogroups.com

> > [mailto:Losmandy_users@yahoogroups.com]

> > > On Behalf Of ericwbenson

> > > Sent: Monday, April 17, 2006 1:43 PM

> > > To: Losmandy_users@yahoogroups.com

> > > Subject: [Losmandy_users] PE improvement

> > >

> > >

> > > I have just uploaded the latest results from my on going battle

> > with

> > > improving the tracking of my G11 (please see PEC saga.doc in

the

> > files

> > > section). Things are much better than when I started, but still

> not

> > > quite good enough, i.e. I still get trails on 20/30 sec

> exposures

> > with

> > > an autoguider running. (NB I know I am pushing the limits since

> I'm

> > > imaging at 0.66"/pixel)

> > >

> > > It seems I have eliminated the largest source of error. The

> > > 76sec 'sorta' periodic peaks that are due to ball bearing

> > compression

> > > in the worm bearing blocks. Diggin thru archives here and on

the

> > net

> > > in general this has been solved before.

> > >

> > > My fix was to use a Dremel tool to enlarge the bearing holes

> with a

> > > 0.625" disk (lucky me, the bearing are 0.625" OD). The disk

> > consists

> > > of a cylindrical piece of rough sand paper over a solid rubber

> > > cylinder. The top 80% of the depth takes less than 2 seconds at

> > > 2500RPM, but the disk tappers slightly so it doesnt grind out

> the

> > > bottom. So the last 20% near the bottom was done by turning the

> > disk

> > > by hand for 5-10 min.

> > >

> > > I replaced the bearings with stock McMaster-Carr ABEC5 bearings

> > (SR4ZZ

> > > I think) (5$ each). The original bearing had to be knock out

> with

> > 3/8"

> > > diameter bolt and hammer, they were that tight! To get the

> bearing

> > out

> > > of the far block (wrt the motor) I had to drill thru the back

> side

> > of

> > > the block with a 3/8" bit.

> > >

> > > Now my biggest concern are the recurrent jumps in the tracking

> that

> > > seem quite periodic. Does anyone know what these are from? What

> > > possible solutions I might try? Or is it hopeless and this is

> what

> > > I've got. Is anybody else willing to post track logs or PEMpro

> > results

> > > so that I might know what is achievable?

> > >

> > > One thing I might try next is to put the helical coupler back

> on,

> > also

> > > I think I might swap the worms again to see if the

> characteristic

> > > jumps change.

> > >

> > > Thanks for listening,

> > > Eric

> > >

> > >

> > >

> > >

> > >

> > > _____

> > >

> > > YAHOO! GROUPS LINKS

> > >

> > >

> > > .

> > > *. Visit your group "Losmandy_users

> > > groups.yahoo.com/group/Losmandy_users> " on the web.

> > >

> > >

> > > *. To unsubscribe from this group, send an email to:

> > > Losmandy_users-unsubscribe@yahoogroups.com

> > > mailto:Losmandy_users-unsubscribe@yahoogroups.com?

> > subject=Unsubscribe>

> > >

> > >

> > > *. Your use of Yahoo! Groups is subject to the Yahoo! Terms of

> > Service

> > > docs.yahoo.com/info/terms/> .

> > >

> > >

> > > _____

> > >

> > >

> > >

> > >

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

> > >

> >

>







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

#29502 Apr 18, 2006

With my G11, the RMS error was usually around 1.1-1.5", and PE of

+2/-2.



OAG should eliminate the effects of mirror flop. Do check that both,

the camera and the guider are very firmly attached to the OAG; if

possible, use all screw-in connections. If you use push-fit adapters

with thumb-screws, tighten hard! If you have only one or two thumb

screws, it may be a good idea to install three of them at 120 degree

angles.



You may still want to check the bearings and the grease: anything

can happen in shipping and in use for a few months. There's also

been a report of aluminum shavings in the bearings of a brand new,

recently shipped Titan, so who knows?



Looking at the final PE chart in your document, I'd think that you

should be able to guide and get decently round stars with well-

calibrated guider.



Do you have Gemini? If yes, then I'd suggest you upgrade to Gemini

Level 4 and program PEC with PemPro to see if you can get a much

improved tracking. Since the errors (even the sharp ones) are

periodic, PemPro should be able to handle them.



The nylon disk is the clutch mechanism and works by friction. It

should have no grease or dirt on it, and shouldn't really sound like

anything. As long as it doesn't slip, it shouldn't be the cause of

any tracking errors. If there's something gritty on it, it's

possible that the same substance is on the gear teeth. That could

certainly cause erratic tracking.





Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "ericwbenson" ebenson@...>

wrote: >

> I'm sorry I meant 1.3" RMS, +3.1/-3" PE. The data I gathered the

> night before was essentially the same as last nights run. The

PEMpro > screen shots are in the files section (see PEC saga.doc).

>

> I have a C11 with Taurus Tracker III oag, ST7EI main camera,

SX716usb > guider. When gathering the tracking data I use the ST7EI straight

> through since it's easier to setup, represents the best case

> sceanario etc. The guider exposures have typically been 0.5 to 1

sec > long, the guide rate is as fast as maxim can go, which seems to be

> about every 2 sec even for very short exposures.

>

> The mount was bought brand new in Jan 06, so up to now I figured

the > bearings should be clean and properly greased!!! I took the RA

axis > apart this morning, I saw some dirt on the nylon (?) clutch pad.

When > turning the RA axis, I could imaging hearing a grinding/crackling

> noise, or is it just a swoosh, not sure, dont know what it's

supposed > to sound like.

>

> I just polished the RA thrust bearing washers, they are certainly

> shinier than before, maybe that will help...

>

> I'm glad to know that 0.5"/pixel is possible. It's funny when I

wrote > the MaxIm AO7 driver years ago we used to kid around how it made

so > many bad mounts look good, but didnt do much adaptive

optic "seeing > fixing". Now that I'm blessed with a mount that is not doing what

I > want, I feel what many people must have felt before when eyeing

the > AO7 unit. Too bad my ST7 only has one chip.

>

> Eric B.

>

> --- In Losmandy_users@yahoogroups.com, "Paul K" pkane2001@> wrote:

> >

> > Eric,

> >

> > 1.3" PE is very good, unless there are random errors or the

> tracking

> > rate is off. Can you please post a Pempro chart showing the data

> > you've gathered?

> >

> > It's easy enough to check if the gear is the problem: simply

slew > to

> > another part of the sky in RA, then move the telescope back by

hand > > to to the starting point: you'll now be using a different part

of > > the gear.

> >

> > There are four other bearings in the axis assembly that may be

> > stuck, dirty, or just need new grease. It may be worth a check

if > > you see random errors.

> >

> > I successfully and consistenly took 20 minute exposures at

> > 0.5 "/pixel with the mount performance as shown in that chart,

so I > > am fairly sure it's doable ;-)

> >

> > Oblong stars could also be the result of flexure or mirror flop.

> > What telescope and guiding setup are you using? How frequent are

> > your guider exposures? What guide rate are you using?

> >

> > Regards,

> >

> > -Paul



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