RCOS field rotator unable to correct PA error

Here is the log file

The rotator goes back and forth between two incorrect position angles, completely missing the proper position angle each time. It is unable to apply the correct delta rotation to the rotator. Any idea what is going on?

It looks to me like there is a bug in the handoff of the rotator delta. Here are the steps occuring:

  1. rotator is at 271, target is 299
  2. rotator delta is calculated to be 28
  3. rotator slews to absolute position of 28
  4. rotator error is calculated as 89
  5. rotator slews to 360-89
  6. rinse and repeat

SGP is asking the rotator to go to the degree angle of the delta, instead of applying the delta

The problem is even more specific actually, the rotator initial commands are usually always 60 degrees off. I posted this in an earlier thread noting how my images post meridian flip were always off by 60 degrees rotation. There is something wrong happening in the math when SGP communicates a rotation error to the RCOS rotator program. This is really hindering our ability to image. Can someone look into this math error?

Any response on this? It severely impacts our capability to do automated imaging. The rotator works in every other program, CCDAP, ACP, etc. I need the capabilities of SGP but this is a huge hinderance.

It sounds like the direction of rotation is reversed as to what SGP is expecting. Can you reverse the rotation direction of the rotator in the ASCOM driver?


No sadly there isn’t an option to reverse it in the ASCOM driver. I’m not entirely sure it is a wrong direction problem. The rotator is capable of going to the correct PA but only when the rotator starts at a PA of 0

It sounds like it is moving in the opposite direction than what we’re expecting which is problematic when applying the offset. The same math is applied to all rotators so I have a hard time believing that this is something specific to the RCOS as we have no direct RCOS implementation for this rotator. Especially if it’s working for other platforms it seems to me that we almost certainly need to enable some sort of reversing directly in SGP to handle this case.