Pier flip before meridian crossing is not possible with SGP and Mach1

Leo Shatz

I recently contacted SGP forum after dealing with aftermath of pier collision after failure to perform auto flip. I think I've sorted out most of the things and I have now solution in hand, but I thought that it's still worth while to raise the following issue with you, too.

If I understand correctly, Mach1 can perform pier flip safely when it stays withing meridian limits as defined in APCC, which include both sides of meridian. However SGP does NOT support flips (either manual or auto) when mount hasn't yet crossed meridian. When I raised a question about supporting pier flips before crossing meridian on SGP forum, there was one answer so far I got from the SGP forum thread on this issue:

"AIUI SGP will flip before the meridian by using the ASCOM set pier side command. The ASCOM driver must report CanSetPierSide as true and implement the PierSide set method. If set PierSide command is sent when the mount can’t do it then the mount should throw an exception. I guess that the AP driver doesn’t do this but can be set so that the hour angle after which a slew will change the pier side is before the meridian. One thing to remember is that SGP is written to work for a multitude of people using a wide variety of mounts."

I'd be glad to know if there is a way to support pier flips before meridian crossing - maybe I'm missing something, or it depends on additional integration between APCC and SGP.



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