Occasional - Guider unexpectedly stopped while waiting for measurement

[Carl Lancaster]

Bob,

I upgraded from ACP 7.1 to 7.2a recently, the installation went without a problem. Prior to the upgrade I began shooting NGC891 and everything worked fine. Several nights ago, after the upgrade, I attempted to shoot NGC891 again with the exact same plan, but this time I started getting this message when attempting to select the guide star for autoguiding, 'Guider unexpectedly stopped while waiting for measurement'. Here is the relavent section of the log file:

02:37:17 Target is now centered.
02:37:18 (long exp(s) or requested, no orbital tracking, trying to autoguide)
02:37:18 Switching from Red to Luminance filter for imaging
02:37:28 (guide star SNR=19.5 X=463 Y=23)
02:37:28 (initial exposure interval 7)
02:37:37 (guide star SNR=21.5 X=463 Y=23)
02:37:37 (final exposure interval 7)
02:37:46 (guide star SNR=18.3 X=464 Y=22)
02:37:46 PA=333 (internal guider @ 0.0 deg)
02:37:47 **Guider unexpectedly stopped while waiting for measurement
02:37:57 (guide star SNR=17.6 X=464 Y=22)
02:37:57 (initial exposure interval 7)
02:38:06 (guide star SNR=18.2 X=465 Y=22)
02:38:06 (final exposure interval 7)
02:38:15 (guide star SNR=18.6 X=464 Y=21)
02:38:15 PA=333 (internal guider @ 0.0 deg)
02:38:16 **Guider unexpectedly stopped while waiting for measurement
02:38:26 (guide star SNR=19.9 X=465 Y=20)
02:38:26 (initial exposure interval 7)
02:38:35 (guide star SNR=19.6 X=465 Y=20)
02:38:35 (final exposure interval 7)
02:38:44 (guide star SNR=20.1 X=465 Y=20)
02:38:44 PA=333 (internal guider @ 0.0 deg)
02:38:45 **Guider unexpectedly stopped while waiting for measurement
02:38:55 (guide star SNR=18.5 X=464 Y=19)
02:38:55 (initial exposure interval 7)
02:39:04 (guide star SNR=18.6 X=464 Y=19)
02:39:04 (final exposure interval 7)
02:39:12 (guide star SNR=18.6 X=464 Y=20)
02:39:13 PA=333 (internal guider @ 0.0 deg)
02:39:14 **Guider unexpectedly stopped while waiting for measurement
02:39:15 **Autoguiding failed.
02:39:15 Doing pointing update to assure guide star on internal/OAG chip
02:39:15 Updating pointing...
02:39:15 Switching from Luminance to Red filter for pointing exposure
02:39:17 (taking 30 sec. exposure, Red filter, binning = 4)
02:39:17 (starting exposure)
02:39:54 (exposure complete and image downloaded)
02:39:55 Image finished
02:39:55 Plate-solve pointing image.
02:39:55 215 image stars found
02:39:55 373 catalog stars found
02:39:56 Solved! 129 stars matched.
02:39:56 Average residual is 0.34 arcsec.
02:39:56 Pointing error is 1.222 arcmin @ angle 91.97
02:39:56 True focal length is 1988.1 mm.
02:39:56 True binned plate scales (arcsec/pix): H = 2.24 V = 2.24
02:39:56 True image center (J2000): 02h 22m 39.6s 42° 20' 47.47"
02:39:56 Imager sky position angle is 333.3 deg.
02:39:56 Rotator mech. position angle is 325.0 deg.
02:39:56 [sync] telescope synced
02:39:56 Within max error tolerance, no re-slew needed.
02:39:56 Target is now centered.
02:39:56 (autoguider still running...)

I went and then manually set the guidestar in Maxim DL and it tracked OK after that. There looked to be plenty of guide stars to pick from in the autoguider image.

Here are the specs for my equipment:

Main Camera: QSI683wsg
Autoguide Camera: SBIG ST-i monochrome
Maxim DL version: 5.23

I did see the following note on the Product Changes and Improvements section for 7.2:

6. Guide star selection now rejects saturated guide stars. Along with this, other improvements and refactoring were made. It now uses the new and improved PSF detector to find stars in the image.

Any ideas??

Thanks.

Carl Lancaster
Riverside, CT

[Bob Denny]

Can you watch it while it's doing this? I think MaxIm is giving a "guide star faded" message? I see that it is picking the same guide star each time it tries to start guiding. It looks PLENTY strong (SN of 19). Is your minimum guide interval 7 sec?

[Carl Lancaster]

Bob,

Yes, the minimum guide interval is set to 7. I don't recall seeing the 'guide star faded' message. I did not get a snapshot of the full autoguider image, but I do recall seeing that in addition to the star it was trying to select there a fair number of easily visible stars to choose from.

I think it is going to be overcast tonight, but tomorrow night looks promising, I should be able to try again then.

Any thoughts as to why it worked with 7.1 but not 7.2a?

Thanks.

Carl

[Bob Denny]

Any thoughts as to why it worked with 7.1 but not 7.2a?

Not offhand. The guide star is clearly being unambiguously selected (same XY coordinates throughout) and has a high SNR. Does this happen all the time or just on this specific target? I know this setup/target worked before. Were you able to watch last night?

[Carl Lancaster]

Bob,

Sorry for not getting back sooner. On Saturday night I tried running a plan with two separate objects, NGC7331 (with a P.A. of 0 degrees) and M76 (with a P.A. of 12 degrees). Both worked fine. So I just ran M76 for the rest of the night and did not get back to the object in question, NGC891. I did note that the P.A for that object is 333.3, I am starting to wonder if I might have a cabling problem with the camera turned at that position. Everything is tied down tight to the autoguider, but I want to check if anything is looks funny with the camera turned at that angle. Tonight the weather looks bad, tomorrow night or Wednesday might work weather wise. I will keep you posted.

Thanks again.

Carl

[Bob Denny]

Ok, it does look like a good star is there, so just watch and see if you can see anything,

[Peter Prendergast]

I have sen this problem so I don't think its your cabling, on the other hand it doesn't happen often. Even if the next plan is the SAME object, things usually run just fine. I have a gut feeling this is a MaximDL issue, I have seen this for several ACP builds it is neither more or less common, but generally is neither fatal or frequent.
Peter

[Carl Lancaster]

Peter,

Thanks for weighing in on this. The cable idea was me sort of grasping at straws. The fact that I can manually track on the guidestar after ACP gives up and begins imaging suggests that it is not the cable. The only other thing I could think of was the position angle, for the object in question it was 333.3 degrees, a pretty steep turn for the rotator. It does not make a lot of sense to me that that would be it, but it might be worth trying a little experimentation for lack of any other ideas.

I am just going to do some straight shooting tonight of M76 since that seems to be working, I might be able to play around with it tomorrow night.

Thanks.

Carl

[Michael Bushell]

hi,

I am getting a strange message when I run a plan from ACP using acquireimage. When it gets to the point where it starts autoguiding it takes the usuals two images in MAxim but after each one this message is displayed in the log window in ACP: "Guider unexpectedly stopped while waiting for measurement". Guiding is that stopped and tracking is turned off. I can go into Maxim and acquire an image, click on a star and guide on it fine. But ACP won't guide. The odd thing is that sometimes it works and sometimes it doesn't, even using the same plan script. Does anyone have a clue what this might be?

Thanks,
Mike

[Bob Denny]

Can you post an ACP Run log from a run that fails? Please attach it rather than pasting <— link to attaching instructions