Rotator, Acquire Star, Positioning, and Guiding Issues

[andyschlei]

I had my first night with ACP last night and it went well. I did follow the user guide "getting started" very closely, and got most things set up well. As I went to use my Pyxis rotator and execute a plan, I had some trouble. I have looked everywhere but can't figure out where I went wrong.

Here is the full story, since that might point to where I am going wrong.

When I did the first simple one-object run in Getting Started, I got an error that the filter was not specified. This was remedied by adding a filter directive. Once the script ran, it imaged OK but did not center the object, it was off by ~arcmin. Other than that, all items passed with flying colors.

I then went to use the rotator. I created a plan using ACP Planner, capturing the FOV and the position angle from The Sky. I followed the set-up instructions for the rotator. Initially, PA 0 solved to about a PA of 100 in Pinpoint. When I executed the plan for the first time, the rotator moved to it's 270, then did an Acquire Star autofocus.

Here occured problem number 1: The star wasn't centered and when Focus Max tried to bump the mount (ACP Scope Hub connected to AP-900) the mount didn't move. Eventually, the focus succeeded.

Here is the log from that point

07:13:46 Autofocus finished.
07:13:51 Start slew to Deer Lick and Stephan 5...
07:13:52 (no rotate, already close enough to desired PA)
07:13:52 (wait for slew to complete)
07:14:00 (slew complete)
07:14:00 (doing post-focus pointing update...)
07:14:00 Updating pointing...
07:14:00 (taking 10 sec. exposure, Luminance filter, binning = 1)
07:14:19 Image finished
07:14:19 Plate-solve pointing image.
07:14:19 806 image stars found
07:14:19 1245 catalog stars found
07:14:20 Solved! 256 stars matched.
07:14:20 Average residual is 0.39 arcsec.
07:14:20 Pointing error is 7.749 arcmin @ angle 144.03
07:14:20 True focal length is 54.5 cm.
07:14:20 True image center (J2000): 22h 37m 13.3s 34° 06' 45.78"
07:14:20 Imager sky position angle is 190.7 deg.
07:14:20 Rotator mech. position angle is 270.0 deg.
07:14:20 [sync] pointing model updated
07:14:20 Internal guider, always re-slew
07:14:20 Re-slew to target.
07:14:20 Start slew to Deer Lick and Stephan 5...
07:14:21 (wait for slew to complete)
07:14:29 (slew complete)
07:14:29 PA error of 79.8 deg. detected. Correcting...
07:14:29 Start rotate to PA 270.5 deg (raw rotator angle 349.8)
07:14:29 (wait for rotator)
07:14:40 (rotation complete)
07:14:40 Target is now centered.

At this point the target was not centered, but I didn't know that yet. At this point, autoguiding failed and the script aborted. I manually re-calibrated autoguiding in Maxim, restarted the script, and acquired the first image. When ACP checked positioning after the first image, it was 18 arcmin off. It recentered and took the second image. This one was 15 degrees off of the position angle in the plan (plan said 270, ACP reported 285). At this point the object was too high.

I tried again with M31, with a new plan. Similar problems.

1. Focus Max bumps don't reposition star (no discrenable movement in scope)
2. ACP solves, moves, then rotates, leaving the image in the wrong position
3. Autoguiding fails. I calibrated using the script in ACP, and it worked until the rotator moved. I noted that the manual angle in Maxim's manual config was outside of its acceptable limit of +/- 180.

I moved the rotator so that its PA of zero was almost exactly actual PA of zero, but that didn't help. I'd also like to move it back because this is a bad position logistically for cables. At this point it was about 2am and I was getting foggy.

I've searched and read but can't figure out where to look next. I must be doing something wrong but can't figure out what it is.

I've put the logs from last night here:ftp://obsballona.net/ACPHelp090815/20090814/

Thanks in advance,

--Andy

[andyschlei]

Update.

The Acquire Star problem is resolved. I unchecked the "sync" option in acquire star set-up in FocusMax and it works fine now. The only thing is ACP appears to override the setting in FocusMax to recenter the original object after completing the focus run. It does the return slew, but does not correct that slew.

Positioning on imaging still has issues. On the first image of a sequence, the position is poor. ACP notices that after the first image is taken, and then corrects it. It would be nice for pointing to be fully evaluated before the first image is taken.

Rotator positioning is an issue. It also has a problem working with autoguiding. Here is what happened last night.

1. Set the rotator to PA 0, which solves to 0 degrees in PinPoint
2. Ran the calibrate guider script, checking guiding, all OK
3. Ran a plan with a PA of 270, it started fine, but autoguiding didn't work. The guider just drove the image off the chip, somehow no adjustment had been made to reflect the change in position angle.
4. Stopped the plan and manually calibrated the guider in Maxim (telescope looking east).
5. Restarted the plan. On initial pointing evaluation, the rotator rotated 180 degrees to 90 degrees (no change to plan or anything else). Autoguiding failed.
6. Stopped and restarted the plan. On initial pointing evaluation, the rotator moved back to 270 (calculated PA was 278). Autoguiding went fine (after all, I had calibrated at that angle).
7. After completing the luminance frames, decided to forgo the color and take a couple more luminance frames and turn in.
8. Modified the plan to omit other colors but left PA and position in the plan the same. When I restarted the plan, the rotator moved again, to an actual position angle of 301 degrees. Interestingly, autoguiding worked this time.

To summarize, the problems with the rotator are:

• Does not consistently establish imaging position
• Does not communicate to autoguider to reflect change in position angle

I am not sure what I have set-up wrong, but it must be something.

Thanks in advance for the help.

--Andy

[Jim McMillan]

Hi Andy,

Before diving into rotator issues, can we start with guiding first. Since you got the luminance working, I might guess that guide star isn't bright enough to use filters...

So, first, what happens when you calibrate and guide in MaxIm only with a clear filter? Then, using the same guide star, what happens when you use the various filters...and at what exposure do you need to use to get reliable results for that mag guide star? Only when you've got this well understood should you add ACP into the mix.

Once ACP is in the mix, first start by figuring out whether you (ACP, really) are able to reliably put the desired guide star on the chip at various PA's. (Suggestion, don't have FM do anything with respect to centering, etc. Your AP 900 mount should do just fine and ACP's centering will be to < 0.1 arcmin accuracy.) The work you do above with respect to guide star mag will help you choose the right guide stars.

Once you've got that working, ACP should automatically deal with changing the guider angle so that guiding works regardless of the PA.

Let us know how your testing progresses.

Good luck.

Jim

[andyschlei]

Jim,

Thanks for the help!

Before diving into rotator issues, can we start with guiding first. Since you got the luminance working, I might guess that guide star isn't bright enough to use filters...

So, first, what happens when you calibrate and guide in MaxIm only with a clear filter? Then, using the same guide star, what happens when you use the various filters...and at what exposure do you need to use to get reliable results for that mag guide star? Only when you've got this well understood should you add ACP into the mix.

Maxim guided fine with filters (even Ha) on the guide stars I was using for my imaging. Guide exposures were about 1 second and as long as 3 seconds for Ha. In all cases where I had a problem, the exposure was 1 second.

In addition, the guiding troubles all occurred at the start of the run with the luminance imaging. Properly calibrated, guiding works fine.

Once ACP is in the mix, first start by figuring out whether you (ACP, really) are able to reliably put the desired guide star on the chip at various PA's. (Suggestion, don't have FM do anything with respect to centering, etc. Your AP 900 mount should do just fine and ACP's centering will be to < 0.1 arcmin accuracy.) The work you do above with respect to guide star mag will help you choose the right guide stars.

Mount and PA positioning have been an issue, as I noted in my second post. After the first exposure of a run, ACP would report a positioning error and re-position the mount. It also did not consistently position the rotator, moving it between re-starts of the same run.

In any case, I am imaging with an ST-10 and NP-101, so the large field of view I have includes many guide star alternatives. (As an aside, I have had enough guide star alternatives that Maxim gets confused while calibrating, picking another star as the moved calibration star. But I digress...) I will both double-check my polar alignment and reset and re-run the pointing adjustment routine the next time I'm at the observatory.

Once you've got that working, ACP should automatically deal with changing the guider angle so that guiding works regardless of the PA.

The adjustment of the calibration based on guider angle is not working for some reason. I calibrated (using the ACP script) at zero PA. Moving to an image at PA 270, the guider marches the star off the chip. I re-calibrated at the new PA and guiding worked perfectly. I consistenly re-created this phenomenon over two nights at a variety of PAs and targets.

Interestingly, the values in Maxim's angle box for manual guider configuration was -277 in one case, matching the calculated value from ACP. Maxim only allows +/- 180 in that field. I had to modify it to hit OK. I had the dialog open to adjust the calibration time. I assume that ACP plugged that value in there. Could that be a bug? In writing this it strikes me that, by coincidence, I did not select a PA below 180 degrees. That would be a worthwhile test.

Thanks again for your response. I'd be interested in any ideas on what to look at regarding the PA communication to Maxim for autoguiding. I still assume that I have something configured incorrectly.

Clear skies,

--Andy

[Jim McMillan]

Hi Andy,

One quick question: what version of MaxIm are you using?

Jim

[andyschlei]

Jim,

One quick question: what version of MaxIm are you using?

I am using Maxim DL 5.0.7.

Clear skies,

--Andy

[Bob Denny]

Jim has kindly provided me with some analysis. I'll work on this ASAP.

[andyschlei]

If it would help I can post logs from my second night or extract the relevant examples from the logs. I also have the images taken if that would help.

--Andy

[Bob Denny]

Post the entire logs by attaching them to your reply here.

[andyschlei]

Post the entire logs by attaching them to your reply here.

The logs from my second night of testing are attached. Here's what's in each:

20090816@053309.log
Acquire Star did not center star. This script was aborted to solve that problem. Guider had been calibrated at the final PA.

20090816@054512.log
Acquire Star works fine (sync turned off in FocusMax). Guider had been calibrated at PA 0 using guider calibration script.

Testing of autoguiding and reading user guide. Re-calibrate guider at PA zero and start again.

20090816@060446.log
First run after calibrating autoguider at PA 0. ACP correctly moves to object, rotates, but guiding fails, script aborted.

Guider manually calibrated and tested at correct (last set) PA.

20090816@061800.log
At start of plan, rotator moves 180 degrees off of target, guiding fails, script aborted.

20090816@061948.log
Restart of plan, rotator moves to correct position, guider calibration matches rotator position without adjustment. First exposure is 18 arcmin off center, corrected after first exposure. Script aborted at start of red exposures, it was getting late.

20090816@065018.log
Modified plan for more luminance, but plan shut down due to safety settings.

20090816@065117.log
Restart after modifying safety settings. ACP moves rotator slightly, and guiding works.

The logs from the first night are here: ftp://obsballona.net/ACPHelp090815/20090814/ I can annotate them if that would help. But the second night's set is probably the cleanest.

Thanks!

--Andy