I am trying to track down an intermittent slewing error that occurs randomly while I am patrolling for SN. I don't know where the problem is emanating from, ie. ACP , SkyX, Maxim or ASCOM but I am hoping this append will trigger some ideas that I can try next.

Observatory Setup.

ACP V 7.0 (build 3, Production Release V7)

No Hot Fix Installed

Observatory computer - Win7

SkyX V 10.2.0 (Build 6409) - controlling a Paramount ME

Maxim DL V 5.23 + SXV-H9

ASCOM Platform 6 - up todate

Problem Description.

While executing an ACP plan of typically 100 target galaxies about 10% of the slews will fail in the following very specific way.

Example;

The last successfully completed target was at position 21:16:53 +13:16:11.
The next ACP plan target is NGC 7052 at 21:18:33 +26:26:50.
The telescope slews however to 21:16:54 +13:18:51. Basically the same RA and a DEC change of +00:02:40.
No error indications anywhere to suggest anything is wrong.

Each failure always has the same DEC delta of +/- 2:40 from the last target position depending whether the target was higher or lower! This is very strange and so specific I am hoping it will lead to some ideas on where the problem lays.

When this happens the ACP control dialog always shows the correct current position, ie. 21:16:54 +13:19:51 at slew completion. So in theory it should realise that something is wrong having requested a slew to different co-ords?

The FITS header for NGC 7052 however has RA, OBJCTRA, DEC and OBJCTDEC all set to the correct target coords, ie. 21 18 33.00 +26 26 50.00 - which of course does not match the image and is how I picked up that something was wrong. Presumably these fields are written by Maxim?

I have attached a snipped ACP log from my last patrol for a galaxy that failed although there does not seem to be anything in the log to suggest anything wrong has happened!

I have eliminated the following system items which could conceivably contribute to the problem:-
- SkyX does not sleep on minimize
- OpenGL in SkyX is turned off
- The failure occurs with / without a remote desktop connection to the observatory computer

I have only been aware of this problem since I started patrolling a few months ago and that's because you get to compare the patrol image with a saved master image - that's a great way to see that something is wrong

Basically I am out of ideas - and somewhat frustrated - Help!

Phil Russell
Cygnus Observatory, I63
Hampshire, UK

ACP Log

ACP console log opened 23-Sep-2013 20:08:10 UTC
This is ACP version 7.0 (build 3, Production Release V7)
Licensed to Philip Russell
20:08:10 Logging to d:\Astronomy\ACP\ObsControl\Logs\20130923\20130923 @200810.log
20:08:11 Initializing AcquireSupport V7.0.4
20:08:11 Telescope is ACP->TheSky, driver V2
20:08:11 MaxIm DL/CCD is version 5.23
20:08:11 Imager is SX Universal
20:08:11 Guider is SX Universal(External Guide Scope)
20:08:11 Guider plate scale unknown, guided dither with guider pixels
20:08:11 Max unguided exposure 121 sec.
20:08:11 Calculated unbinned plate scales (arcsec/pix): H = 0.72 V = 0.72
20:08:11 Calculated field of view (arcmin): H = 16.7 V = 12.5
20:08:11 Using focus offsets and star mags from FilterInfo.txt
20:08:12 Scope cannot be synced, so all-sky solving is not useful
20:08:12 This is AcquireImages V7.0.2
20:08:12 Hardware pier side reporting is available.
20:08:12 Compiling plan...
20:08:12 (using ACP Plan Compiler V7.0.1)
20:08:12 ...plan OK!
20:08:12 == Resuming interrupted plan ==
20:08:12 This plan has 123 live target(s), 123 images
20:08:12 There are 61.5 min. of actual imaging time
20:08:12 Image file set-numbers start with 1
20:08:12 Periodic auto focus every 30 min.
20:08:12 (includes a plan-start auto focus)
20:08:12 Automatic pointing updates are disabled
20:08:12 (plate solving is disabled)
20:08:12 Starting run for plan ACP-Skyx-SNP-2100-2200+00-60-15.0.txt...
20:08:12 Autofocus will be done every 30 min.
20:08:12 ==== Starting target PGC 65877 ====
20:08:16 (no slew, scope already within max error of target)
20:08:16 Ready for PGC 65877 (# 2 of 123 in set 1)
...
snip
...
21:14:20 Calibrating image...
21:14:20 Start slew to PGC 66936...
21:14:22 Image finished
21:14:25 ==== Starting target PGC 66936 ====
21:14:29 Start slew to PGC 66936... PJR>>>>>>>>>>>>>>>>> PGC 66936 slews correctly
21:14:30 (wait for slew to complete)
21:14:34 (slew complete)
21:14:34 Ready for PGC 66936 (# 72 of 123 in set 1)
21:14:34 Selecting C filter (0) for imaging
21:14:38 [flip check: Tn=330s HAc=-709s GW=F HAz=-379s DWz=F WF=no]
21:14:38 === Place in plan ===
21:14:38 Set 1 of 1
21:14:38 Target is "PGC 66936" (72 of 123)
21:14:38 Repeat 1 of 1 for this target
21:14:38 Filter C (1 of 1)
21:14:38 Image 1 of 1 for this filter
21:14:38 Imaging to PGC 66936-S001-R001-C001-C
21:14:38 (taking 30 sec. exposure, C filter, binning = 2)
21:14:38 (starting exposure)
21:15:12 (exposure complete and image downloaded)
21:15:12 Calibrating image...
21:15:13 Start slew to IC 5119... PJR>>>>>>>>>>>>>>>>> Slew to IC 5119 fails - see my append
21:15:14 Image finished
21:15:18 ==== Starting target IC 5119 ====
21:15:22 Start slew to IC 5119...
21:15:23 (wait for slew to complete)
21:15:25 (slew complete)
21:15:25 Ready for IC 5119 (# 73 of 123 in set 1)
21:15:25 Selecting C filter (0) for imaging
21:15:29 [flip check: Tn=330s HAc=-659s GW=F HAz=-405s DWz=F WF=no]
21:15:29 === Place in plan ===
21:15:29 Set 1 of 1
21:15:29 Target is "IC 5119" (73 of 123)
21:15:29 Repeat 1 of 1 for this target
21:15:29 Filter C (1 of 1)
21:15:29 Image 1 of 1 for this filter
21:15:29 Imaging to IC 5119-S001-R001-C001-C
21:15:29 (taking 30 sec. exposure, C filter, binning = 2)
21:15:29 (starting exposure)
21:16:04 (exposure complete and image downloaded)
21:16:04 Calibrating image... PJR>>>>>>>>>>>>>>>>>>>>>> IC 5119 image is incorrect
21:16:04 Start slew to IC 1392... PJR>>>>>>>>>>>>>>>>>>>>>> Slew to IC 1392 is correct
21:16:06 Image finished
21:16:08 ==== Starting target IC 1392 ====
21:16:08 (wait for slew to complete)
21:16:16 (slew complete)
21:16:20 (no slew, scope already within max error of target)
21:16:20 Ready for IC 1392 (# 74 of 123 in set 1)
21:16:20 Selecting C filter (0) for imaging
21:16:24 [flip check: Tn=330s HAc=-774s GW=F HAz=-444s DWz=F WF=no]
21:16:24 === Place in plan ===
21:16:24 Set 1 of 1
21:16:24 Target is "IC 1392" (74 of 123)
21:16:24 Repeat 1 of 1 for this target
21:16:24 Filter C (1 of 1)
21:16:24 Image 1 of 1 for this filter
21:16:24 Imaging to IC 1392-S001-R001-C001-C
21:16:24 (taking 30 sec. exposure, C filter, binning = 2)
21:16:24 (starting exposure)
21:16:58 (exposure complete and image downloaded)
21:16:58 Calibrating image...
21:16:58 Start slew to PGC 67025... PJR>>>>>>>>>>>>>>>>>>>>>> Slew to PGC 67025 is correct
21:17:00 Image finished
21:17:03 ==== Starting target PGC 67025 ====
...
snip PJR>>>>>>>>>>>>>>>>>>>>>> (10-15) other failures occurred
...
22:07:53 Image finished
22:07:56 (turning tracking off for safety)
22:07:58 End of run.
ACP console log closed 23-Sep-2013 22:07:58 UTC