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1100AE mediocre guiding
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Dick C
---------- Forwarded message --------- From: Dick C <dixiemail123@...> Date: Tue, Mar 21, 2023 at 9:57 AM Subject: 1100AE mediocre guiding To: <main+owner@ap-gto.groups.io> Ok, guys, I ran my 140mm refractor on the mount unguided last night for 20 minutes per Brian's and Roland's suggestion, using Guiding Assistant. Attached is the log file. 1. I re aligned the PA just before doing this; NINA said I was within 15 arc secs of the pole; Guide Assistant said I was off by 8.6 arc minutes!! Who is right? According to the log file it looks like NINA is wrong, and by quite a bit?? 2. Recall PHD2 was choosing only saturated guide stars, and I read up on this and found that apparently the default setting for Saturation by Max-ADU Value of 255 was wrong for my ASI 174 guide camera at 16 bits. So I tried "Saturation via star profile", and it chose tiny unsaturated guide stars, but the guiding was worse. Then I read that Max-ADU Value was the better setting but the value should be 65000. So I did that and I got good guide stars after that. But the guiding was still mediocre. Is 65000 the correct value I should use? 3. The seeing was not good last night according to Astrospheric. But with an encoder mount I would have expected lousy seeing would yield guiding of maybe 0.5 a/s accuracy instead of 0.2-0.3 a/s. I got 0.7-0.95 a/s last night, still not what it should be. With an encoder mount I would expect the guide graph would be fairly smooth, small swings, with PHD2 just having to nudge it once in a while. But my graph has violent sharp peaks. Note that the swings on the graph are 2 to 4 a/s, which seems way too much. So PHD2 is dong way too much work. I tried 10 different guide stars, tried aggression from 55% to 100%, exposures of 2 secs to 4 secs, min/move from 15 to 10 (recommended by Guide Assistant). 55% aggression seemed to be less "violent" but the up and down movement of each axis was away from the "zero" line --neither ever going back and touching the line, so I went back to the default of 80%. This made the corrections come closer to the zero line, but still lots of sharp movements with big peaks (2-4 a/s swings up and down). See photo. 4. Per the video on AP's site I changed to Low Pass2 on the algorithms tab (this was not the default in dev4, I can't remember what was). But the video was a while back and for dev1. Should I use a different setting for dev4? What other settings do you recommend to improve the guiding? Thanks Dick |
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Ray Gralak
Hi Dick,
1. I re aligned the PA just before doing this; NINA said I was within 15 arc secs of the pole; Guide Assistant said IA drift measurement (e.g. PHD2) will almost always be more accurate for polar alignment than using several sky points (NINA?). That's because slewing large distances will bring flexure and other pointing errors into the mix. 3. The seeing was not good last night according to Astrospheric. But with an encoder mount I would haveAre you using a pointing model? If not, telescope pointing errors, such as polar misalignment and flexure, can cause considerable drift, which will factor into the guiding results. You can mitigate this with a pointing model using APCC Pro that came with your mount. Also, your particularly bad seeing may be from a local heat source, like nearby concrete and roofs, and even your telescope if it is not at ambient temperature. Dew heaters on the main telescope can be especially troublesome if you are using a guide scope, as at times it may be looking through the heat plumes from the dew heater. -Ray |
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Cheng-Yang Tan
Hi Dick, There's something wrong. Can you post a photo of your set up? To start off, since you say that the PA error in 8.6 arcmin in PHD2 after PA in NINA, I think something actually moved between PA in NINA and PHD2 drift. I use SharpSkyPro for PA and it's always < 5 arcmin in PHD2 drift. Also your guide graph is really bad as well. The only time I've seen something like this happening is when thin wispy clouds are in the FOV of the guidescope (I use an OAG). Did you look at the sky by eyeball or crank up the gain of your guide scope to see whether you're guiding through clouds? cytan
On Tuesday, March 21, 2023 at 09:43:42 AM CDT, Dick C <dixiemail123@...> wrote:
---------- Forwarded message --------- From: Dick C <dixiemail123@...> Date: Tue, Mar 21, 2023 at 9:57 AM Subject: 1100AE mediocre guiding To: <main+owner@ap-gto.groups.io> Ok, guys, I ran my 140mm refractor on the mount unguided last night for 20 minutes per Brian's and Roland's suggestion, using Guiding Assistant. Attached is the log file. 1. I re aligned the PA just before doing this; NINA said I was within 15 arc secs of the pole; Guide Assistant said I was off by 8.6 arc minutes!! Who is right? According to the log file it looks like NINA is wrong, and by quite a bit?? 2. Recall PHD2 was choosing only saturated guide stars, and I read up on this and found that apparently the default setting for Saturation by Max-ADU Value of 255 was wrong for my ASI 174 guide camera at 16 bits. So I tried "Saturation via star profile", and it chose tiny unsaturated guide stars, but the guiding was worse. Then I read that Max-ADU Value was the better setting but the value should be 65000. So I did that and I got good guide stars after that. But the guiding was still mediocre. Is 65000 the correct value I should use? 3. The seeing was not good last night according to Astrospheric. But with an encoder mount I would have expected lousy seeing would yield guiding of maybe 0.5 a/s accuracy instead of 0.2-0.3 a/s. I got 0.7-0.95 a/s last night, still not what it should be. With an encoder mount I would expect the guide graph would be fairly smooth, small swings, with PHD2 just having to nudge it once in a while. But my graph has violent sharp peaks. Note that the swings on the graph are 2 to 4 a/s, which seems way too much. So PHD2 is dong way too much work. I tried 10 different guide stars, tried aggression from 55% to 100%, exposures of 2 secs to 4 secs, min/move from 15 to 10 (recommended by Guide Assistant). 55% aggression seemed to be less "violent" but the up and down movement of each axis was away from the "zero" line --neither ever going back and touching the line, so I went back to the default of 80%. This made the corrections come closer to the zero line, but still lots of sharp movements with big peaks (2-4 a/s swings up and down). See photo. 4. Per the video on AP's site I changed to Low Pass2 on the algorithms tab (this was not the default in dev4, I can't remember what was). But the video was a while back and for dev1. Should I use a different setting for dev4? What other settings do you recommend to improve the guiding? Thanks Dick |
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Ross Salinger
Using two AP encoder mounts and following the recommended video assiduously I’ve never been able to get the guiding on either mount working better as it does with the “standard” PC settings. I assume that’s because I’m making some mistake in my PHD workflow setup. That’s what I think that you are almost certainly doing. However, both mounts do much much better than what you are getting. (They are both in very good to excellent locations, so there’s that.)
One thing that I (think I) gleaned from your log is that you are not using multi-star. This has been the single greatest improvement that I’ve seen in guiding over the past 10 years. Maybe I missed it. Second thing I noticed is that you didn’t calibrate before the session started. The instant I get very poor guiding, I re-calibrate the guiding system at DEC 0 and near the meridian. The eliminates any possibility that I’m using an obsolete calibration. Finally, there should be no material difference between NINA PA and PHD’s numbers. (That’s based on my 3 mounts.) So, I wonder how stable the ground is where you are set up. I could never get good guiding in my backyard until I put down some large pavers.
If this were my mount I’d start by running the guiding assistant and using that to get a standard configuration set up. That should get you much better guiding than what you are getting now. Then save that profile and do the recommended changes and see if that cures your situation. When making changes and getting bad results always consider re-calibrating the system. YMMV of course.
Rgrds-Ross
Sent from Mail for Windows
From: Dick C
Sent: Tuesday, March 21, 2023 7:43 AM To: main@ap-gto.groups.io Subject: [ap-gto] 1100AE mediocre guiding
---------- Forwarded message ---------
Ok, guys, I ran my 140mm refractor on the mount unguided last night for 20 minutes per Brian's and Roland's suggestion, using Guiding Assistant. Attached is the log file.
1. I re aligned the PA just before doing this; NINA said I was within 15 arc secs of the pole; Guide Assistant said I was off by 8.6 arc minutes!! Who is right? According to the log file it looks like NINA is wrong, and by quite a bit??
2. Recall PHD2 was choosing only saturated guide stars, and I read up on this and found that apparently the default setting for Saturation by Max-ADU Value of 255 was wrong for my ASI 174 guide camera at 16 bits. So I tried "Saturation via star profile", and it chose tiny unsaturated guide stars, but the guiding was worse. Then I read that Max-ADU Value was the better setting but the value should be 65000. So I did that and I got good guide stars after that. But the guiding was still mediocre. Is 65000 the correct value I should use?
3. The seeing was not good last night according to Astrospheric. But with an encoder mount I would have expected lousy seeing would yield guiding of maybe 0.5 a/s accuracy instead of 0.2-0.3 a/s. I got 0.7-0.95 a/s last night, still not what it should be. With an encoder mount I would expect the guide graph would be fairly smooth, small swings, with PHD2 just having to nudge it once in a while. But my graph has violent sharp peaks. Note that the swings on the graph are 2 to 4 a/s, which seems way too much. So PHD2 is dong way too much work. I tried 10 different guide stars, tried aggression from 55% to 100%, exposures of 2 secs to 4 secs, min/move from 15 to 10 (recommended by Guide Assistant). 55% aggression seemed to be less "violent" but the up and down movement of each axis was away from the "zero" line --neither ever going back and touching the line, so I went back to the default of 80%. This made the corrections come closer to the zero line, but still lots of sharp movements with big peaks (2-4 a/s swings up and down). See photo.
4. Per the video on AP's site I changed to Low Pass2 on the algorithms tab (this was not the default in dev4, I can't remember what was). But the video was a while back and for dev1. Should I use a different setting for dev4? What other settings do you recommend to improve the guiding?
Thanks
Dick
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Dick C
There is no "reply" button on my screen (despite the documentation saying there is) so to reply I'll have to send a new post. Thanks for the helpful comments: I do have "use multi-stars" checked. My mount is on heavy pavers. There is no flex, everything seems rigid. There were no clouds, wispy or otherwise visible, and Clear Outside showed a forecast of zero clouds at all levels all night. So I don't think it was clouds. The final guide star it used didn't drop off for 4 hours, and with clouds it usually does. Yes my cable management needs improvement, but there were no catches or tangles. "
I’d start by running the guiding assistant and using that to get a standard configuration set up". That's exactly what I've done. Twice. Now I did move the mount 30 feet across the yard and used the same calibration, because the current location of the mount has trees blocking the meridian/celestial equator. (And the guiding was worse the night before I moved it, with calibration done near the meridian/celestial equator.) So I could try to redo the calibration, altho the mount doesn't know it's been moved, and I haven't told PHD2. I don't think 30 ft will make a difference as to how the stars move, and to do a new calibration from its current location would have to be high in the east, --less than ideal. But I could try that. The difference in PA from NINA to PHD2 is puzzling. I did the PA facing north, looking right at Polaris, which should have been ideal, but I will redo the PA high in the east tonight to see if that helps. It is true I have a dew heater strip on the main objective and the guide scope sees over that, so that could be a factor.
That's a likely suspect,
so I'll turn it off tonight and see if that makes a difference. I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding", creating those huge swings on the graph. What other settings should I try? |
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Cheng-Yang Tan
I'd recommend housekeeping first. IMO, consistent guiding < 0.5 arcsec *requires* no drag from cables or anything else. Here's my setup (not the latest, but close enough) without anything dangling.  This setup can get me < 0.3 arcsec *if* the seeing is good. And the seeing outside my house is never that great but it's good enough to consistently guide below < 0.5 arc. with 0.3 to 0.4 arcsec being typical. I know you say that everything is rigid, but between PHD2 and NINA, the difference in PA is large and I still hypothesize that something has to have flexed. I assume the AP1100 is not your first mount, so have you ever seen this problem before between PHD2 and NINA on your previous mount? When you lose a guide star in PHD2, that's when the clouds are really thick. I've imaged through wispy clouds and it wasn't obvious that I did. Here's a photo of M13 and the wispy clouds I had imaged through:   The wispy cloud image was taken with my PoleMaster which I had mounted on the saddle plate (See photo). I use it to both do initial PA and also to monitor sky conditions. The gain was cranked up and integration time was at least 1 s to even see these clouds. And I think I remember that the only reason why I took this picture was that guiding was crappy. I probably have the PHD2 guide graph somewhere if I can find it. cytan
On Tuesday, March 21, 2023 at 12:57:23 PM CDT, Dick C <dixiemail123@...> wrote:
There is no "reply" button on my screen (despite the documentation saying there is) so to reply I'll have to send a new post. Thanks for the helpful comments: I do have "use multi-stars" checked. My mount is on heavy pavers. There is no flex, everything seems rigid. There were no clouds, wispy or otherwise visible, and Clear Outside showed a forecast of zero clouds at all levels all night. So I don't think it was clouds. The final guide star it used didn't drop off for 4 hours, and with clouds it usually does. Yes my cable management needs improvement, but there were no catches or tangles. "
I’d start by running the guiding assistant and using that to get a standard configuration set up". That's exactly what I've done. Twice. Now I did move the mount 30 feet across the yard and used the same calibration, because the current location of the mount has trees blocking the meridian/celestial equator. (And the guiding was worse the night before I moved it, with calibration done near the meridian/celestial equator.) So I could try to redo the calibration, altho the mount doesn't know it's been moved, and I haven't told PHD2. I don't think 30 ft will make a difference as to how the stars move, and to do a new calibration from its current location would have to be high in the east, --less than ideal. But I could try that. The difference in PA from NINA to PHD2 is puzzling. I did the PA facing north, looking right at Polaris, which should have been ideal, but I will redo the PA high in the east tonight to see if that helps. It is true I have a dew heater strip on the main objective and the guide scope sees over that, so that could be a factor.
That's a likely suspect,
so I'll turn it off tonight and see if that makes a difference. I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding", creating those huge swings on the graph. What other settings should I try? |
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Ross Salinger
Leaving aside the remote possibility that the mount needs adjusting or that the seeing was really bad, calibration is the most important thing I can suggest.
Other than that, the general rule in guiding is that you don’t want to see “swings”. That’s often a sign that there is poor seeing and the solution is to reduce the aggression quite a bit. I would note with that the two AP mounts that I use (both belong to friends) I set the aggression to 50 percent in both axes. But again, these are pier mounted and located in Bortle ¾ skies.
When using the NINA PA, try to use the default setting which will slew the mount to near the celestial pole. From memory I recall having some issues when I tried to use it at lowish declinations but others may disagree.
Otherwise I’m stumped.
Rgrds-Ross
Sent from Mail for Windows
From: Dick C
Sent: Tuesday, March 21, 2023 10:57 AM To: main@ap-gto.groups.io Subject: [ap-gto] 1100AE mediocre guiding
There is no "reply" button on my screen (despite the documentation saying there is) so to reply I'll have to send a new post.
Thanks for the helpful comments:
I do have "use multi-stars" checked. My mount is on heavy pavers. There is no flex, everything seems rigid. There were no clouds, wispy or otherwise visible, and Clear Outside showed a forecast of zero clouds at all levels all night. So I don't think it was clouds. The final guide star it used didn't drop off for 4 hours, and with clouds it usually does.
Yes my cable management needs improvement, but there were no catches or tangles.
" I’d start by running the guiding assistant and using that to get a standard configuration set up". That's exactly what I've done. Twice.
Now I did move the mount 30 feet across the yard and used the same calibration, because the current location of the mount has trees blocking the meridian/celestial equator. (And the guiding was worse the night before I moved it, with calibration done near the meridian/celestial equator.) So I could try to redo the calibration, altho the mount doesn't know it's been moved, and I haven't told PHD2. I don't think 30 ft will make a difference as to how the stars move, and to do a new calibration from its current location would have to be high in the east, --less than ideal. But I could try that.
The difference in PA from NINA to PHD2 is puzzling. I did the PA facing north, looking right at Polaris, which should have been ideal, but I will redo the PA high in the east tonight to see if that helps.
It is true I have a dew heater strip on the main objective and the guide scope sees over that, so that could be a factor. That's a likely suspect, so I'll turn it off tonight and see if that makes a difference.
I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding", creating those huge swings on the graph. What other settings should I try?
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Ray Gralak
Hi Dick,
I do have "use multi-stars" checked. My mount is on heavy pavers. There is no flex, everything seems rigid. ThereIn the unguided Phd2 log you posted earlier, the guide star was bouncing around quite a bit in Declination and Right Ascension, which could contribute to the autoguiding behavior you are seeing. Also, in case you are doing this, do not walk near your setup while autoguiding. Besides wafting off body heat, each step may cause low-frequency vibrations that might be visible in autoguiding data - even with a pier, as you have. -Ray |
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Roland Christen
Do 5 to 10 minutes of guiding with the guide commands turned off. See what the guider graph looks like. You cannot make any conclusions about the mount with guider corrections on. Turn off the guide pulses and record the RA and DEC graph - take a screen shot, it will tell everything you need to know about the seeing at your location. You can then proceed from there. Until you do that, nobody will be able to help you.
Roland
-----Original Message-----
From: Dick C <dixiemail123@...> To: main@ap-gto.groups.io Sent: Tue, Mar 21, 2023 4:43 am Subject: [ap-gto] 1100AE mediocre guiding ---------- Forwarded message ---------
From: Dick C <dixiemail123@...> Date: Tue, Mar 21, 2023 at 9:57 AM Subject: 1100AE mediocre guiding To: <main+owner@ap-gto.groups.io> Ok, guys, I ran my 140mm refractor on the mount unguided last night for 20 minutes per Brian's and Roland's suggestion, using Guiding Assistant. Attached is the log file.
1. I re aligned the PA just before doing this; NINA said I was within 15 arc secs of the pole; Guide Assistant said I was off by 8.6 arc minutes!! Who is right? According to the log file it looks like NINA is wrong, and by quite a bit??
2. Recall PHD2 was choosing only saturated guide stars, and I read up on this and found that apparently the default setting for Saturation by Max-ADU Value of 255 was wrong for my ASI 174 guide camera at 16 bits. So I tried "Saturation via star profile", and it chose tiny unsaturated guide stars, but the guiding was worse. Then I read that Max-ADU Value was the better setting but the value should be 65000. So I did that and I got good guide stars after that. But the guiding was still mediocre. Is 65000 the correct value I should use?
3. The seeing was not good last night according to Astrospheric. But with an encoder mount I would have expected lousy seeing would yield guiding of maybe 0.5 a/s accuracy instead of 0.2-0.3 a/s. I got 0.7-0.95 a/s last night, still not what it should be. With an encoder mount I would expect the guide graph would be fairly smooth, small swings, with PHD2 just having to nudge it once in a while. But my graph has violent sharp peaks. Note that the swings on the graph are 2 to 4 a/s, which seems way too much. So PHD2 is dong way too much work. I tried 10 different guide stars, tried aggression from 55% to 100%, exposures of 2 secs to 4 secs, min/move from 15 to 10 (recommended by Guide Assistant). 55% aggression seemed to be less "violent" but the up and down movement of each axis was away from the "zero" line --neither ever going back and touching the line, so I went back to the default of 80%. This made the corrections come closer to the zero line, but still lots of sharp movements with big peaks (2-4 a/s swings up and down). See photo.
4. Per the video on AP's site I changed to Low Pass2 on the algorithms tab (this was not the default in dev4, I can't remember what was). But the video was a while back and for dev1. Should I use a different setting for dev4? What other settings do you recommend to improve the guiding?
Thanks
Dick
-- Roland Christen Astro-Physics |
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Roland Christen
Forget all that. Do a 5 minute run with guide pulses turned off! Then show that guider graph with the pulses off. It will tell you and us definitively what is really going on. Everything else will flow from that.
Ro0land Christen
Astro-Physics Inc. -----Original Message-----
From: Dick C <dixiemail123@...> To: main@ap-gto.groups.io Sent: Tue, Mar 21, 2023 7:57 am Subject: [ap-gto] 1100AE mediocre guiding There is no "reply" button on my screen (despite the documentation saying there is) so to reply I'll have to send a new post.
Thanks for the helpful comments:
I do have "use multi-stars" checked. My mount is on heavy pavers. There is no flex, everything seems rigid. There were no clouds, wispy or otherwise visible, and Clear Outside showed a forecast of zero clouds at all levels all night. So I don't think it was clouds. The final guide star it used didn't drop off for 4 hours, and with clouds it usually does.
Yes my cable management needs improvement, but there were no catches or tangles.
"
I’d start by running the guiding assistant and using that to get a standard configuration set up". That's exactly what I've done. Twice.
Now I did move the mount 30 feet across the yard and used the same calibration, because the current location of the mount has trees blocking the meridian/celestial equator. (And the guiding was worse the night before I moved it, with calibration done near the meridian/celestial equator.) So I could try to redo the calibration, altho the mount doesn't know it's been moved, and I haven't told PHD2. I don't think 30 ft will make a difference as to how the stars move, and to do a new calibration from its current location would have to be high in the east, --less than ideal. But I could try that.
The difference in PA from NINA to PHD2 is puzzling. I did the PA facing north, looking right at Polaris, which should have been ideal, but I will redo the PA high in the east tonight to see if that helps.
It is true I have a dew heater strip on the main objective and the guide scope sees over that, so that could be a factor.
That's a likely suspect,
so I'll turn it off tonight and see if that makes a difference.
I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding", creating those huge swings on the graph. What other settings should I try?
-- Roland Christen Astro-Physics |
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Dick C
Here are a couple screen shots of my unguided graph. About 20 min using Guiding Assistant in PHD2.  Obviously my PA was off, despite my getting it to within 20 a/s or so with NINA's 3 point star alignment. This is puzzling, as the following night I redid the PA and it was indeed off as much as Guiding Assistant said. Dunno how that happened. All I did after PA-ing in NINA was slew to an area high in the east and run Guiding Assistant. Somehow the PA changed a lot from that slew. Anyway, I'll fix that by making sure everything is tight next time. The second screen shot below zoomed in shows unguided RA varied by 2.5 a/s or so, which surprises me; I thought an encoder mount would do better, but perhaps it was because, again, the PA changed with that slew and I was not PA'd as I thought I was.  |
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Hi Dick Can you please upload your log for this - screenshots aren't very helpful for analysis, thanks On Wed, Mar 22, 2023 at 8:16 AM Dick C <dixiemail123@...> wrote:
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Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com |
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steve.winston@...
>I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding"
So the answer is Yes to the above, you need to be using lowpass2 for both RA and DEC. Is that what you're using? |
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>>>>I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding" Here is a little background that may help understand PHD guiding for encoder mounts Originally Roland (and others) coined the phrase 'bump guiding' to indicate the preferred way to use guiding software with an encoder mount. Myself and others added to and refined the approach, but it was clear that additional PHD2 features could make this easier. We contacted the authors of PHD2 and worked to add features specifically for optimizing using guiding with AE mounts, and tested it thoroughly with multiple AP mounts. The result was the features added PHD2 in version 2.6.11 dev 1 (and of course later versions have this as well) We made a video to explain how best to use guiding with encoder mounts (once again link here :) https://youtu.be/wCu8PKjDZ20 ) To sum it up, the encoder-specific features and settings in PHD2, the approach on how to use them, and the AP 'how to' video aren't "sort of" an idea on how to use guiding with encoder mounts. They are features put into PHD2 at our suggestion, and exactly the recommendation and approach authored and validated by AP users. Anyone using an AE mount with PHD2 should be following those guidelines unless you have a specific reason not to. Brian On Wed, Mar 22, 2023 at 9:02 AM <steve.winston@...> wrote: >I think more important would be things like "should PHD2 to be set to the Lowpass2 algorithms" or some other algorithms, and things like that. It seems like PHD2 was working way too hard "overguiding" --
Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com |
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Roland Christen
It's very hard to see your image scale, however it appears that you have some bouncing around of the guide star in both axes. The amount of motion in Dec from a straight line will describe the amount of seeing error on your system. Unfortunately the Dec axis is drifting too much to be able to tell exactly how much star motion you are getting.
If we assume that you have not inadvertently turned off the encoders, then we could judge the star motion (seeing error) from that axis to be about 2 arc sec P-V. There also may be some tugging on the axis by cables as the mount tracks, which could explain the star's motion in RA near the beginning of your run. If you are using a separate guide scope, make sure that the scope and camera are very well fixed and cannot move. Also the cables from the back of the guide camera must be fixed in place so they cannot cause any kind of movement of the camera or guide scope. It doesn't take much to get 2 arc sec error with cables not tight - it's only a few microns which you won't see via eyeballing it.
Looking at the first graph, it appears the encoders are engaged since the tracking with encoders off would have a repeating sinusoidal shape, not the small random motions that your RA track shows. When you say that the 2.5 arc sec tracking of the encoder mount surprises you, but what you are seeing is the motion of a star, not the motion of the mount axis. If the star moves randomly in the sky, the mount cannot know that and correct it without getting proper feedback from a guider system. That's why I had you do 10 minutes of tracking with the guider correction off - so we can see what the motion of the guide star is.
One thing that occurred to me is that you may be trying to guide at a slower rate than 1x sidereal. Please check that you are setting the guide rate at 1x sidereal. Also, make sure that you set the guide parameters using the focal length of you guide scope, not your main scope.
That's all I can deduce right now, not having the Dec track side by side with the RA. Dec is important because it will show the minimum amount of star motion below which you cannot improve regardless of how you try to chase the seeing. Once you know the magnitude of the seeing error you can set the Min Move at approximately 75% of that value so that the guider won't try to chase random star motions.
Roland Christen
Astro-Physics Inc. -----Original Message-----
From: Dick C <dixiemail123@...> To: main@ap-gto.groups.io Sent: Wed, Mar 22, 2023 5:16 am Subject: [ap-gto] 1100AE mediocre guiding Here are a couple screen shots of my unguided graph. About 20 min using Guiding Assistant in PHD2.
 Obviously my PA was off, despite my getting it to within 20 a/s or so with NINA's 3 point star alignment. This is puzzling, as the following night I redid the PA and it was indeed off as much as Guiding Assistant said. Dunno how that happened. All I did after PA-ing in NINA was slew to an area high in the east and run Guiding Assistant. Somehow the PA changed a lot from that slew. Anyway, I'll fix that by making sure everything is tight next time.
The second screen shot below zoomed in shows unguided RA varied by 2.5 a/s or so, which surprises me; I thought an encoder mount would do better, but perhaps it was because, again, the PA changed with that slew and I was not PA'd as I thought I was.
 -- Roland Christen Astro-Physics |
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Roland Christen
Hi Brian,
Roland -----Original Message-----
From: Brian Valente <bvalente@...> To: main@ap-gto.groups.io Sent: Wed, Mar 22, 2023 5:18 am Subject: Re: [ap-gto] 1100AE mediocre guiding Hi Dick
Can you please upload your log for this - screenshots aren't very helpful for analysis, thanks
On Wed, Mar 22, 2023 at 8:16 AM Dick C <dixiemail123@...> wrote:
Brian
Brian Valente
astro portfolio https://www.brianvalentephotography.com/astrophotography/
portfolio brianvalentephotography.com
-- Roland Christen Astro-Physics |
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Yes I can see your analysis Roland The logs will help answer the follow-on questions (guidespeed, any calibration issues, orthogonality error, etc.) that naturally come from seeing the unguided results teamwork! Brian
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Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com |
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Hi Dick
Ray pointed out you posted the guidelogs at the start, my apologies for missing this. You do appear to be guiding at 1.0x sidereal, which is good If you moved your mount, you will need to re-check polar alignment and re-calibrate your guider. It may not seem to make a difference, but it can and in your case it probably does The two main issues I see in your guiding results are - significant polar misalignment (all of your dec guide pulses are in one direction, the 'smoking gun' of polar misalignment) - corrections in RA and Dec are identical mirrors of each other, which suggests your mount has changed enough that the guiding calibration was invalidated hth Brian |
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