Help Requested with Gemini Mount Flipping

[Robert Brewington]

OK, I am having some odd issues, and I think some of it is related to flipping the mount. Reviewing my logs, I am a bit confused.

I started the evening with a target which I believe was just west of the meridian. ACP shows WEST in the display, but the OTA is on the west side of the mount, tilted below 180 of level.
- I think WEST means the OTA is looking to the west of meridian? How can I tell if the OTA is on the West or East side? I would have thought that the initial slew to the target would put the OTA on the East side, looking WEST. However, the system rarely seems to do that. It prefers to tilt the OTA pretty far past meridian.

As the evening went on, the mount never flipped. I "think" it eventually hit the safety limit on the mount; one image shows the stars as "trails" about 50 arcminutes long in the RA direction, as though it stopped tracking. The flip check lines are

02:27:10 [flip check: Tn=660s HAc=2517s GW=T HAz=3178s DWz=F WF=no]
02:30:04 [flip check: Tn=2160s HAc=2692s GW=T HAz=4852s DWz=F WF=no]
02:30:44 [flip check: Tn=2100s HAc=2725s GW=T HAz=4832s DWz=F WF=no]
03:02:47 [flip check: Tn=2100s HAc=4655s GW=T HAz=6760s DWz=F WF=no]
03:34:05 [flip check: Tn=2100s HAc=6536s GW=T HAz=8643s DWz=T WF=no]
04:05:42 [flip check: Tn=0s HAc=7803s GW=T HAz=8444s DWz=T WF=no]
04:07:04 [flip check: Tn=2100s HAc=7877s GW=T HAz=10626s DWz=T WF=no]
04:40:15 [flip check: Tn=2100s HAc=9873s GW=T HAz=12622s DWz=T WF=no]
05:12:55 [flip check: Tn=2100s HAc=11839s GW=T HAz=14586s DWz=T WF=no]


Not sure what these mean. GW=T means the mount is on the west? This matches what I experienced - the OTA stayed on the Wets side all night. It sounds like Tn is the time until the mount needs to flip? If so, wouldn't it steadily decrease until the mount flips? Not sure what else these lines tell me. Do these lines make sense?

My flipConfig.txt is the default one, 300 PreFlip, 120 post flip.


Also, the log has messages "**SYNC ACROSS FLIP POINT FOR GERMAN MOUNT. SYNC SKIPPED" when it does the pointing correction. Don't really know what this is telling me - is it a bad thing?


Perhaps related - the Autoguiding was not what I expected. I did a Calibration in Maxim, checked guiding worked, OK (looking East, OTA on west side). Then when ACP ran, the target was just west of meridian, OTA still on the West side, and the guiding tracked the guide star off the chart. I then checked "Pier Flip" in Maxim and re-ran the ACP plan, whereupon the guiding worked correctly. This also didn't make sense to me.


Lastly, I think an easy question: when autoguiding fails (due to dim star, I think I have a cloud) ACP decides to stop autoguiding and expose without guiding. This isn't going to work - I am doing 30 minute exposures, they aren't going to work without guiding. I thought I saw a setting somewhere about this, but I can't find it now. Seems like I want to either a) wait for awhile and try autoguiding again (maybe the cloud has passed) or b) wait awhile then move on to the next exposure. Anyone know where this setting is? Can I detect guide failure in the middle of an exposure and recover by restarting the exposure once guiding is working again?

I am attaching the entire log in case anyone wants to look it over for other things I should be seeing

Thanks,
brew

[Bob Denny]

What do you mean "on the west"? Looking west or mechanically on the west (the opposite)? I'm short on time right now, but I'll look at this later today or on Wednesday (I am out tomorrow) sorry...

[Robert Brewington]

Sorry, I'm trying to be specific without knowing the exact words I'm trying to consistently refer to the OTA position as being on the east or west side of the mount.

I don't exactly know what the WEST indicator on the ACP display means. Watching the mount and watching the indicator, at first I thought it was the opposite of the OTA position. I.e., WEST meant the OTA was on the East side, looking toward the West. However, now WEST "seems" to mean that the OTA is looking at a target on the West side of the meridian, but the OTA could be on either the East or the West side of the mount. I may be wrong about that.

For example, generally I expect the OTA to be on the East side of the mount looking at a target to the West. However, it often seems that the OTA is on the West side looking at a Western target; in this case, the mount is tipped so the OTA is below the counterweights. The OTA kind of looks like it is getting upside-down. This was the starting position when I started the run.

I understand that during an imaging run we can often continue tracking past the meridian East to West (and this is a Good Thing). However, it seems odd to have the initial slew position in that manner, as though we had just continued past the meridian.


When looking at the Flip Check info, the GW=T seemed to mean Gem on the West = True. I don't know what would trigger the flip to make it go over to the east side (OTA to the East, looking West). It seems to just keep tipping farther and farther over, leaving the OTA on the West side the entire time. My log never showed an attempt to flip. Maybe I am not doing enough new targets (re-focus, pointing updates, etc) to cause a re-slew which would flip the mount.

I have found, for example, that if I slew all around the sky to different targets, it wants to keep the OTA on the same side of the mount. Example:
- suppose the OTA is on the East side (looking West)
- I slew to look at target X, on the East of the meridian.
- it will keep the OTA on the East by tipping it below the counterweights.
- If I aim at a target even farther (lower) to the East, the OTA now flips to the West side.
- Once it flips, if I again slew to look at target X (still in the East), now the OTA is on the West as expected.

I don't expect this is wrong behavior, I just don't understand the pattern or what to expect. I thought the flip check information would clarify the situation, but not yet

Don't know if I have clarified the situation or not

[Bob Denny]

I am out of time for today. The Gemini has been a chronic source of frustration to me for years. I don't own one and can't understand the myriad of settings in the current Gemini driver.

What ACP expects is: If you slew to a target west of the meridian (or flip point) the mount/OTA will be on the east, looking west. When you slew to a target east of the meridian (or flip point) ACP expects the mount/OTA to be on the west, looking east. Whether it can track past the flip point is irrelevant for slew operations.

Your mount seems to be set up not to behave this way, and that would be responsible for several types of errors including guiding problems, wrong rotator operation, etc.

Is there someone here who uses the Gemini that can help Brew? I would be so appreciative (and so would he!). I'm moving this to the Hardware/Drivers section since it is not related to ACP (other than ACP expecting the mount to behave like most GEMs).

[Bob Denny]

Yeah, looking again, something is wrong with how the mount is acting with regards to flips. I might suggest you post this to the Gemini ASCOM Driver group at

http://tech.groups.yahoo.com/group/Gemini_ASCOM_Driver/

maybe someone will know what setting or settings affect this.