Adjust RA tracking rate
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Yann-Eric Boyeau
Hi everybody,
I am a new mesu/sitech user. I had 2 difficult first nights with the mount learning how it works.
Last setup 0.92ge fixed my phd2 dec guiding rate being twice the RA rate. (0.92ge should be advertised on official website...)
Made my first guided subs 0,5” RMS🤩 not bad ! But corrections in RA were all in the same direction...
My polar alignment error is less than 10 ‘’ and my focal length is 630mm.
Testing unguided (but tracking on) 10min sub, I noticed trailed stars (70” long).
So I read this thread : https://stargazerslounge.com/topic/247247-mesu-200-ra-guide-speed-correction/ I understand this solution but now I have a question :
Is there a better way to adjust RA tracking speed without « cheating » with the number of ticks ?
I read about rate OFFSET in sitech manual, is it the way to adjust RA tracking rate ? How does it works ?
Thanks a lot for your help,
Yann Turns out that I had an issue with a loose screw on a gear! And maybe some other mechanical issues. I’m back to a working scope again, but I could really use some help. What are the top 5 things I need to know to get decent accuracy in Go-To? Right now my PXP RMS error is around 13 arc minutes, maximum 20. But I can’t hit an object unless I first do an offset-init on a star within 5 degrees of my target.
-Rob Brown
From:
SiTechservo@... [mailto:SiTechservo@...]
I have built an alt-az mount for my 12.5" scope. Until recently, it was working in Go-To (but not well). Then suddenly it is off by tens of degrees in Go-To. Tracking is working acceptably well.. I've read the Scitech manual but I am lost. Is there anyone in the Portland Oregon area willing to spend an evening with me going through the calibration and setup? The Moon is up, so it wouldn't be like giving up a dark night! There is so much to learn!
-Rob Brown
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Don W
Hi Yann, A new mount should track properly. The Mesu mounts are very good and very popular. However I don't have one, so my answer is general to you. Tracking rate depends on both time and tic setting in SiTech. So first, make sure your PC clock is accurate and the setting in your SiTech Features/Offset Tracking Rates has the Servo Clock Cal set to 0.99995. Then watch the "Diff between Computer Time and Scope Time. That value should stay low (±10 ms) and not climb (either positive or negative). The clock built-in to the controller is very accurate. Some PC clocks are not very accurate - the "fix" is to resynch the PC clock with a time server regularly. I use a program called "Master Synch" and have it update my PC every increment (MasterSynch can do it every 15 seconds or set to minutes or hours). But that needs internet access. The process in your reference article at Stargazerslounge is a way to reset the tics/rev to get accurate tracking if your clock is OK or adjusted automatically with Master Synch. With an accurate clock AND any adjustment per the Stargazerslounge article, you should be able to track for minutes with little error. There is one other caveat: Checking the tracking rate for accuracy requires checking it over an RA period. If your mount has periodic error you must check tracking over that entire period. I don't know what the Mesu period is. The best way I know to check the periodic error is using PemPro with your camera. Then Pempro can create a PEC correction to the SiTech tracking to minimize PE. SiTech has the settings for Offst Tracking Rate which is easy to use. You measure the amount of tracking error in arc-sec for a period of time (like 10 minutes) and use the SiTech program to calculate the correction. This is primarily for tracking moving objects like comets or asteroids, not for overall tracking. So in summary, Check your PC clock, check the Clock Calibration setting, Measure the tracking error for one full period, Run Pempro for multiple periods (Pempro will show you any drift error) and possible use the PemPro PEC curve to adjust your tracking. Note that using a periodic error correction needs a sensor on the RA drive to set the synchronization with SiTech. Don W ---In SiTechservo@..., <yann_eric_boyeau@...> wrote : Hi everybody, I am a new mesu/sitech user. I had 2 difficult first nights with the mount learning how it works. Last setup 0.92ge fixed my phd2 dec guiding rate being twice the RA rate. (0.92ge should be advertised on official website...)
Made my first guided subs 0,5” RMS🤩 not bad ! But corrections in RA were all in the same direction...
My polar alignment error is less than 10 ‘’ and my focal length is 630mm.
Testing unguided (but tracking on) 10min sub, I noticed trailed stars (70” long).
So I read this thread : https://stargazerslounge.com/topic/247247-mesu-200-ra-guide-speed-correction/ I understand this solution but now I have a question :
Is there a better way to adjust RA tracking speed without « cheating » with the number of ticks ?
I read about rate OFFSET in sitech manual, is it the way to adjust RA tracking rate ? How does it works ?
Thanks a lot for your help,
Yann |
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yann_eric_boyeau
Hi Don, Thank you very much for your answer and advices. As described, I am very new to the Sitech controller and also to my new friction drive mount. I guess that multiple factors can make the mount track not as accurately as I wish for the moment (clock, ticks, scope setup, driver configuration, PA, flexion, mechanical or electronic issues,...). I am discovering a lot a things to learn and to take into account before modifying anything to the factory configuration. I am confident that any anomaly has always a logical explanation. As you suggested, I checked if the Clock was OK. Attached is a capture of the offset tracking window, showing Diff between Computer Time and scope time after 1 hour of operations. Would you confirm the clock was OK ? If that is OK, I will continue to narrow my investigations for better tracking. Considering PEC, I am not sure if it applies to Mesu mounts (no worm drive but possible slip with friction, I do not have absolute encoders), I will check that with Lucas Mesu. Thanks again a lot for your help, Yann ---In SiTechservo@..., <westergren@...> wrote : Hi Yann, A new mount should track properly. The Mesu mounts are very good and very popular. However I don't have one, so my answer is general to you. Tracking rate depends on both time and tic setting in SiTech. So first, make sure your PC clock is accurate and the setting in your SiTech Features/Offset Tracking Rates has the Servo Clock Cal set to 0.99995. Then watch the "Diff between Computer Time and Scope Time. That value should stay low (±10 ms) and not climb (either positive or negative). The clock built-in to the controller is very accurate. Some PC clocks are not very accurate - the "fix" is to resynch the PC clock with a time server regularly. I use a program called "Master Synch" and have it update my PC every increment (MasterSynch can do it every 15 seconds or set to minutes or hours). But that needs internet access. The process in your reference article at Stargazerslounge is a way to reset the tics/rev to get accurate tracking if your clock is OK or adjusted automatically with Master Synch. With an accurate clock AND any adjustment per the Stargazerslounge article, you should be able to track for minutes with little error. There is one other caveat: Checking the tracking rate for accuracy requires checking it over an RA period. If your mount has periodic error you must check tracking over that entire period. I don't know what the Mesu period is. The best way I know to check the periodic error is using PemPro with your camera. Then Pempro can create a PEC correction to the SiTech tracking to minimize PE. SiTech has the settings for Offst Tracking Rate which is easy to use. You measure the amount of tracking error in arc-sec for a period of time (like 10 minutes) and use the SiTech program to calculate the correction. This is primarily for tracking moving objects like comets or asteroids, not for overall tracking. So in summary, Check your PC clock, check the Clock Calibration setting, Measure the tracking error for one full period, Run Pempro for multiple periods (Pempro will show you any drift error) and possible use the PemPro PEC curve to adjust your tracking. Note that using a periodic error correction needs a sensor on the RA drive to set the synchronization with SiTech. Don W ---In SiTechservo@..., <yann_eric_boyeau@...> wrote : Hi everybody, I am a new mesu/sitech user. I had 2 difficult first nights with the mount learning how it works. Last setup 0.92ge fixed my phd2 dec guiding rate being twice the RA rate. (0.92ge should be advertised on official website...)
Made my first guided subs 0,5” RMS🤩 not bad ! But corrections in RA were all in the same direction...
My polar alignment error is less than 10 ‘’ and my focal length is 630mm.
Testing unguided (but tracking on) 10min sub, I noticed trailed stars (70” long).
So I read this thread : https://stargazerslounge.com/topic/247247-mesu-200-ra-guide-speed-correction/ I understand this solution but now I have a question :
Is there a better way to adjust RA tracking speed without « cheating » with the number of ticks ?
I read about rate OFFSET in sitech manual, is it the way to adjust RA tracking rate ? How does it works ?
Thanks a lot for your help,
Yann |
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yann_eric_boyeau
Sorry, there was something wrong with the attachment (png?), I put it again in jpg.
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Don W
Hi Yann, Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good. The Mesu mounts are good mounts. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage. DonW ---In SiTechservo@..., <e3ad7z7aiwpi5iyohdqhrb5wjciot6nitjrqvamb@...> wrote : Sorry, there was something wrong with the attachment (png?), I put it again in jpg. |
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Yann-Eric Boyeau
Hi Don,
My time difference is very small =2.3,6.7mS. mSOffset=-26 So I am now confident that my Clock is OK.
Mesu are really good mounts, that’s why I was surprised it did not manage to get better tracking.
As clock is good, I am now checking if any slippage. I think that is easy to test, even during daytime : I just need to track RA for hours and check the angle difference between encoders of the scope and of the motor. I found that the sitechExe logging options were very good.
If time is OK and there is no slippage during tracking, I will adjust the tick numbers to adjust RA tracking speed if needed.
I will also have a check at Periodic Error.
Thanks a lot for your useful information,
Yann
De : SiTechservo@... [mailto:SiTechservo@...]
Hi Yann,
Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good.
The Mesu mounts are good mounts. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage.
DonW
Sorry, there was something wrong with the attachment (png?), I put it again in jpg.
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How about OTA/focuser flexure as a source of tracking
error?
-Christopher Erickson
Observatory engineer Summit Kinetics From: SiTechservo@... [mailto:SiTechservo@...] Sent: Monday, June 4, 2018 6:19 PM To: SiTechservo@... Subject: RE: [SiTechservo] Re: Adjust RA tracking rate Hi Don,
My time difference is very small =2.3,6.7mS. mSOffset=-26 So I am now confident that my Clock is OK.
Mesu are really good mounts, that’s why I was surprised it did not manage to get better tracking.
As clock is good, I am now checking if any slippage. I think that is easy to test, even during daytime : I just need to track RA for hours and check the angle difference between encoders of the scope and of the motor. I found that the sitechExe logging options were very good.
If time is OK and there is no slippage during tracking, I will adjust the tick numbers to adjust RA tracking speed if needed.
I will also have a check at Periodic Error.
Thanks a lot for your useful information,
Yann
De :
SiTechservo@... [mailto:SiTechservo@...]
Hi Yann,
Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good.
The Mesu mounts are good mounts. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage.
DonW
Sorry, there was something wrong with the attachment (png?), I put it again in jpg. |
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Yann-Eric Boyeau
Hi,
Yes, that something more to add to my check list !
I am not sure if such flexures could lead to 20 s tracking errors on 10 min subs because the scope stay nearly in the same position during a 10 min move, But I will make some more tests considering flexure.
Thank you for bringing this to my attention
Yann
De : SiTechservo@... [mailto:SiTechservo@...]
How about OTA/focuser flexure as a source of tracking error?
-Christopher Erickson Waikoloa, HI 96738
From:
SiTechservo@... [mailto:SiTechservo@...]
Hi Don,
My time difference is very small =2.3,6.7mS. mSOffset=-26 So I am now confident that my Clock is OK.
Mesu are really good mounts, that’s why I was surprised it did not manage to get better tracking.
As clock is good, I am now checking if any slippage. I think that is easy to test, even during daytime : I just need to track RA for hours and check the angle difference between encoders of the scope and of the motor. I found that the sitechExe logging options were very good.
If time is OK and there is no slippage during tracking, I will adjust the tick numbers to adjust RA tracking speed if needed.
I will also have a check at Periodic Error.
Thanks a lot for your useful information,
Yann
De :
SiTechservo@... [mailto:SiTechservo@...]
Hi Yann,
Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good.
The Mesu mounts are good mounts.. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage.
DonW
Sorry, there was something wrong with the attachment (png?), I put it again in jpg.
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Yann-Eric Boyeau
hi everybody,
I am still trying to understand why my mount tracks slower than expected.
After rather good (but not perfect) polar alignment, I started guiding during several hours.
This endend in good guiding results (mesu is well known for this) BUT during all the session my RA corrections were all in the same direction.
Looking at my PHD log, measured drift endend in a approx 6" /min drift error (see attachment) : that means my mount tracked at 0.9 sideral rate.
I think my encoders ticks count can not be 10% off, that would be a very big error in ticks determination.
Do you think my 0.9 measured tracking speed may be related to the 0.9 "gain" value configured in sitech controller ?
Thanks,
Yann-Eric
From: SiTechservo@... on behalf of 'Christopher Erickson' christopher.k.erickson@... [SiTechservo]
Sent: Tuesday, June 5, 2018 15:26 To: SiTechservo@... Subject: RE: [SiTechservo] Re: Adjust RA tracking rate
How
about OTA/focuser flexure as a source of tracking error?
-Christopher Erickson
Observatory engineer Summit Kinetics From: SiTechservo@... [mailto:SiTechservo@...] Sent: Monday, June 4, 2018 6:19 PM To: SiTechservo@... Subject: RE: [SiTechservo] Re: Adjust RA tracking rate Hi Don,
My time difference is very small =2.3,6.7mS. mSOffset=-26 So I am now confident that my Clock is OK.
Mesu are really good mounts, that’s why I was surprised it did not manage to get better tracking.
As clock is good, I am now checking if any slippage. I think that is easy to test, even during daytime : I just need to track RA for hours and check the angle difference between encoders of the scope and of the motor. I found that the sitechExe logging options were very good.
If time is OK and there is no slippage during tracking, I will adjust the tick numbers to adjust RA tracking speed if needed.
I will also have a check at Periodic Error.
Thanks a lot for your useful information,
Yann
De : SiTechservo@... [mailto:SiTechservo@...]
Hi Yann,
Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good.
The Mesu mounts are good mounts.. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage.
DonW
Sorry, there was something wrong with the attachment (png?), I put it again in jpg.
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Don W
Hi Yann-Eric, No the gain setting only controls the correction of a detected error in tracking by correcting in your case 90% of the error (when there is an error). In your case the tracking speed is too slow. Your controller is issuing not enough tics per unit of time. It is alright to change your tics/rev setting to compensate (or correct) your current setting. Multiply your current tics/rev for RA by 1+1/9 = 1.111 and try that tracking. This should get you much closer to accurate tracking. You won't hurt anything doing this, and you can always go back or adjust to a new setting to get the tracking as accurate as possible. The most accurate tracking at true sidereal rate is near the zenith. Tracking at lower altitude angles will have refraction effects which change the tracking rate of the local sky. Generally check your tracking at more than 45° high and best along or near the meridian. Don W ---In SiTechservo@..., <yann_eric_boyeau@...> wrote :
hi everybody,
I am still trying to understand why my mount tracks slower than expected.
After rather good (but not perfect) polar alignment, I started guiding during several hours.
This endend in good guiding results (mesu is well known for this) BUT during all the session my RA corrections were all in the same direction.
Looking at my PHD log, measured drift endend in a approx 6" /min drift error (see attachment) : that means my mount tracked at 0.9 sideral rate.
I think my encoders ticks count can not be 10% off, that would be a very big error in ticks determination.
Do you think my 0.9 measured tracking speed may be related to the 0.9 "gain" value configured in sitech controller ?
Thanks,
Yann-Eric
From: SiTechservo@... <SiTechservo@...> on behalf of 'Christopher Erickson' christopher.k.erickson@... [SiTechservo]
<SiTechservo@...>
Sent: Tuesday, June 5, 2018 15:26 To: SiTechservo@... Subject: RE: [SiTechservo] Re: Adjust RA tracking rate
How
about OTA/focuser flexure as a source of tracking error?
-Christopher Erickson
Observatory engineer Summit Kinetics From: SiTechservo@... [mailto:SiTechservo@...] Sent: Monday, June 4, 2018 6:19 PM To: SiTechservo@... Subject: RE: [SiTechservo] Re: Adjust RA tracking rate Hi Don,
My time difference is very small =2.3,6.7mS. mSOffset=-26 So I am now confident that my Clock is OK.
Mesu are really good mounts, that’s why I was surprised it did not manage to get better tracking.
As clock is good, I am now checking if any slippage. I think that is easy to test, even during daytime : I just need to track RA for hours and check the angle difference between encoders of the scope and of the motor. I found that the sitechExe logging options were very good.
If time is OK and there is no slippage during tracking, I will adjust the tick numbers to adjust RA tracking speed if needed.
I will also have a check at Periodic Error.
Thanks a lot for your useful information,
Yann
De : SiTechservo@... [mailto:SiTechservo@...]
Hi Yann,
Sorry, I don't see the jpg, Yahoo isn't very good about showing attachments. If after an hour your time difference is small, like less than 100 millisecond you are good, if it is thousands then not so good.
The Mesu mounts are good mounts.. The friction drive wheel might have some periodic error - it doesn't take much eccentricity to cause PE. Slippage of friction drives is always a concern but the Mesu mounts do not have a reputation of slippage.
DonW
Sorry, there was something wrong with the attachment (png?), I put it again in jpg.
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Dan Gray
Did you make a telescope model? If so, can you email it to me for a look? If not, you may consider making a model, it may help tracking. Dan On Thu, Jun 14, 2018 at 7:53 PM, westergren@... [SiTechservo] <SiTechservo@...> wrote:
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Don Degidio
Yann,
toggle quoted message
Show quoted text
Can you check the track the drive roller moves is clean and free of any lubricant? Don D ----- Original Message -----
From: "Yann-Eric Boyeau yann_eric_boyeau@... [SiTechservo]" <SiTechservo@...> To: <SiTechservo@...> Sent: Friday, June 01, 2018 5:47 AM Subject: [SiTechservo] Adjust RA tracking rate Hi everybody, |
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