Meridian flip adventures


#1

After the first 100 days with SGP, I think I managed to understand almost all the functions important to me. My setup:

  • Mount: Vixen GP with Skywatcher SynScan GoTo kit upgrade
  • ASCOM Driver: EQMOD
  • Guiding: PHD-2, QHY5L-IIc camera and 60mm f/4 finder
  • Scope: 80mm f/7 ED (f= 552mm)
  • Camera: EOS 1000D
  • Windows 7, 64bit. Locale: German(de)
  • SGP V2.4.1.10

Everything works as expected, except the meridian flip, where a lot of funny and not so funny things happen. Yesterday night I decided to do some tests. The complete log is here:

www.anrs.de/atm/sg_logfile_20150802231620.zip

As it is a bit longish and has lots of sequence aborts, I have extracted and commented a subset of it for just one test-run of the meridian flip:

www.anrs.de/atm/sg_logfile_only_the_flip.zip

Regarding this flip, I have two questions:

  1. The slew goes to a different target as the one indicated by the pre-flip solve:

    [02.08.2015 23:54:49] [DEBUG] [Telescope Thread] Plate solving scope frame successful, scope is synced, writing FITs header info…
    [02.08.2015 23:54:49] [DEBUG] [Telescope Thread] Checking to see if solve might be bad…
    [02.08.2015 23:54:49] [DEBUG] [Telescope Thread] User chose to abort sequence due to bad solve… — This is not true, the user did not do such a thing.
    [02.08.2015 23:54:49] [DEBUG] [Telescope Thread] Telescope: Syncing to J2000 RA: 19,0089804664176 Dec: 33,0324069113262

[02.08.2015 23:54:59] [DEBUG] [Pier Flip Thread] Meridian Flip: Sending Telescope command to execute meridian flip
[02.08.2015 23:54:59] [DEBUG] [Telescope Thread] ASCOM Telescope: Pier side is West
[02.08.2015 23:54:59] [DEBUG] [Telescope Thread] ASCOM Telescope: attempting pier flip using slew
[02.08.2015 23:54:59] [DEBUG] [Telescope Thread] Telescope: Slewing to J2000 RA: 18,8690048106093 Dec: 29,2090110085227

Is this by design? I think it would be more efficient to use the actual target for the flip. The subsequent centering is fortunately done using the original target coordinates.

  1. In the verification and centering frames the stars are more or less trailed in the east-west direction. One example (raw fit-file):

www.anrs.de/atm/FunnySolveFrame01.zip

Some of these frames can be solved by the local all sky solver, but I wonder what coordinates this returns. This might be the reason why the centering did not work but the recovery sequence was able to center, on the first attempt, to better than 10pix.

Anyway, the question is, why the trailing. One possibility is that the time stamps in the log do not reflect the actual order of the events (the slewing and the capture are done in different threads) and the capture starts before the mount reaches the final position. Another possibility is that EQMOD enthusiastically reports “end of slew” to early.

In this context, it might be useful to have a “keep solve frames” flag.

Best regards,
Horia


#2

Yesterday I had the chance to test some more meridian flips and I am happy to announce that it is working without problems. The important parameter have been the “Mount settling time”. Increasing it from 2sec to 30sec just gave the system all the time it needs and the trailing went away. 30sec might be too much but as centering happens only now and then, the time spent here is not that important.

The log file:

www.anrs.de/atm/sg_logfile_20150806002041.zip

While inconsequential, as this will be corrected by the centering loop, the flipping slew is done to the wrong position, somewhere near the actual target. As far as I understand it, this is a bug.

The actual target was:
RA: 20:00:00
DEC: 66° 00’ 00"

What we have is:


[06.08.2015 00:43:52] [DEBUG] [Sequence Thread] Checking if Meridian Flip is needed
[06.08.2015 00:43:52] [DEBUG] [Sequence Thread] Telescope is on the West side of the mount
[06.08.2015 00:43:52] [DEBUG] [Sequence Thread] Meridian Flip needed, Hour Angle >= Degrees Past To Flip: 2,56309034558363 >= 1
[06.08.2015 00:43:52] [DEBUG] [Sequence Thread] Running blocking meridian flip…
[06.08.2015 00:43:52] [DEBUG] [Pier Flip Thread] Meridian Flip: Starting Meridian Flip Procedure
[06.08.2015 00:43:52] [DEBUG] [Pier Flip Thread] Meridian Flip: Calling SGM_TELESCOPE_SOLVE

[06.08.2015 00:44:09] [DEBUG] [Telescope Thread] Plate solving scope frame successful, scope is synced, writing FITs header info…
[06.08.2015 00:44:09] [DEBUG] [Telescope Thread] Checking to see if solve might be bad…
[06.08.2015 00:44:09] [DEBUG] [Telescope Thread] User chose to abort sequence due to bad solve…
[06.08.2015 00:44:09] [DEBUG] [Telescope Thread] Telescope: Syncing to J2000 RA: 20,0012416454938 Dec: 65,9934371576936

[06.08.2015 00:44:15] [DEBUG] [Pier Flip Thread] PHD2: Successfully stopeed PHD2…
[06.08.2015 00:44:15] [DEBUG] [Pier Flip Thread] Meridian Flip: Sending Telescope command to execute meridian flip
[06.08.2015 00:44:15] [DEBUG] [Telescope Thread] ASCOM Telescope: Pier side is West
[06.08.2015 00:44:15] [DEBUG] [Telescope Thread] ASCOM Telescope: attempting pier flip using slew
[06.08.2015 00:44:15] [DEBUG] [Telescope Thread] Telescope: Slewing to J2000 RA: 19,668037045825 Dec: 65,5611328125
[06.08.2015 00:44:15] [DEBUG] [Telescope Thread] Telescope: Slewing to RA: 19,668037045825 Dec: 65,5611328125

[06.08.2015 00:46:35] [DEBUG] [Telescope Thread] Performing auto center step 3 (scope)…
[06.08.2015 00:46:35] [DEBUG] [Telescope Thread] Auto center slewing scope to match reference…
[06.08.2015 00:46:35] [DEBUG] [Telescope Thread] Telescope: Slewing to J2000 RA: 20,0012416454938 Dec: 65,9934371576936
[06.08.2015 00:46:35] [DEBUG] [Telescope Thread] Telescope: Slewing to RA: 20,0012416454938 Dec: 65,9934371576936
[06.08.2015 00:46:40] [DEBUG] [Telescope Thread] Scope reports it is done with synchronous slew, verifying…
[06.08.2015 00:46:40] [DEBUG] [Telescope Thread] Scope has completed slewing

Horia


#3

Sorry I didn’t see this earlier. That is the correct fix for my mount too. It just needs a little time to settle before I let it start plate solving again.

Chris


www.mainsequencesoftware.com