DDM85 and ACP: Pier Flip Settings

[wemartin]

I have read all the explanations, done the tests, tried many combinations but have failed to find the right settings that minimise the waiting time in ACP when the object I am imaging crosses the Meridian.  I am part of a survey consortium looking at particular stars for up to four hours per night total time using a repeating sequence that takes up to five minutes to cycle through.  No individual exposure is longer than 2 minutes.  Needless to say it's very difficult to avoid going through the Meridian with such a long dwell time on a single target. 

 

The minimum delay time ACP inserts is about 40minutes when crossing the Meridian and no exposures are done during this time.  I have set the ACP flip points at zero (flip at the Meridian) and the Track Past at 50min with a 5min assurance time.  I know from testing that the DDM85 will slew to 200min past the Meridian without flipping but I cannot use this as the OTA hits the pier in some configurations.

 

So, I obviously have failed to grasp what ACP, AutoSlew, and the DDM85 are doing at the Meridian with my repeated exposure configuration.  Can someone suggest a set of parameters that will reduce the waiting time?  And why these work?

 

Bill

[wemartin]

This is actually a SideOfPier property reporting fault in AutoSlew. I have confirmed this several ways but the most obvious was today in some slewing tests in daylight. At 15:30 LST slew to 13h RA, 64deg DEC. AutoSlew (and ACP) report pier side is west and the mount is in the west position (counterweight shaft pointing west). Slew to 30h RA, 64deg DEC. AutoSlew (and ACP) report pier side is west but the mount is physically in the EAST position with the counterweight shaft pointing East. So there is a bug in the pier side reporting when the position is North of the Celestial Pole.

 

Bill

[wemartin]

Oops.  Should say 03h RA, 64deg DEC.  Must be early onset Alzheimer's.

 

Bill

[wemartin]

My apologies to all and especially Philipp Keller.  I now know more than I ever wanted to know about German equatorial mounts and SideOfPier considerations.  Finally reading and testing Autoslew and the mount against the ASCOM V2/V3 standard shows that the mount is reporting exactly what it should.  There is no SideOfPier reporting problem.  If you wish to check this yourself and find the very arcane definition that is the SideOfPier property and how it is not the same as the physical side of pier, I attach a short Visual Basic program that runs under ACP scripting that slews in a loop around the Meridian through the zenith and Pole.

 

This has not solved my 17000sec wait for flipping the mount that ACP is generating but, AutoSlew reports correctly when slewing near the Pole in so far as I have been able to test it.  Back to ACP then.

 

Bill

 

 

PierSide3.txt

[wemartin]

And back again to Autoslew.  It seems this problem is a DestinationSideOfPier issue not a SideOfPier issue.  If Autoslew says it can report both SideOfPier and DestinationSideOfPier then ACP uses these for the time to flip calculation.  Apparently the standard and the industry practice on how DestinationSideOfPier is determined can lead to differences which result in bad things about pier flipping times.  These are not likely to arise frequently in normal operation but sadly the survey I am doing ends up with this issue almost every night since I am doing a long series of short exposures around the Pole.  Messy, fixable but only within Autoslew if operation with ACP/Scheduler is expected to go smoothly.

 

Bill