Optec Gemini Focuser & Rotator

Does SGP support the duality of the Optec Gemini Focuser and Rotator?

1 Like

@johnnyK

The Optec Gemini Focusing-Rotator works just fine with SGP. I have been using mine for about 18 months. Since the Gemini has built-in temperature compensation, I allow my Gemini to make continuous focus adjustments. I do not enable TC inside SGP.

Charlie

thanks for the info

I have been using the Gemini for the last several weeks with SGP. I am having some difficulties with the rotator meeting my criterion for <2 degrees. In fact in some runs the best it has been able to do is around 16 degrees.
Could you share your settings or methodology to let me use the rotator more affectively
Thanks

@johnnyK

If you are talking about my SGP settings:

I have the rotator positioning set to 0.2 degrees, which has not been a problem. The Gemini rotator has 6 arc seconds / step, so it can be set pretty accurately. I rarely see more than two attempts needed to meet my centering criteria.

I image with two different scopes (2440mm fl and 680mm fl) but I don’t change the centering criteria when I change scopes.

Charlie

@johnnyK

Your issue sounds like the issue i had when I first stared using the Optec Pyxis Rotator. The reverse direction was checked in the Optec ASCOM driver. I believe it was not in SGP but in the Optec Pyxis ASCOM driver configuration files. what I found is that you DO NOT want any reverse direction checked in either SGPro or Pyxis ASCOM for the Optec rotator. Once I fixed that in my setup I’ve never had any other issues with the rotator. Not sure if this is what your issue is as your rotator is a different model.

Mark

Thanks for the feed back.
My Gemini keeps moving and never seems to get to the proper position during the plate solve.
Do you set the rotator to a position for startup in the initial setup “set rotator to positon” or ignore that input?
I will look at my Gemini configuration to se if anything looks funny in the native driver setup.

I’ll take a look at the native driver for the Gemini and see if this option is incorrect.
Thanks

Did you set any parameters in the Gemini configuration sw to sync with SGP? When I used SkyX with the Gemini it knew where it was relative to the sky. Since I use a different ASCOM driver with SGP (AP ASCOM) I am not sure how the rotator knows where it is or how it reads the position of the image from the Plate Solver. I am using Platesolve 2 in SGP.

Thanks for your consideration

JK

@johnnyK

I don’t have access to my observatory computer but I am pretty sure the Gemini needs the “reverse” option checked. When I first started using the Gemini, I remember having issues of it not going where I wanted it to. I noticed that when I had it set to 270 degrees and told it (via SGP) to go to 260 degrees, it ended up going to 280. It took a while for it to sink in that it had moved the requested 10 degrees – just in the wrong direction. So, check the “reverse” option in the Gemini software but not in SGP.

One other important issue I should have mentioned before – DO NOT attempt to set the Sky Position Angle in Gemini Commander. ONLY use SGP to move the rotator. My startup procedure is:

  1. Home the rotator and ignore the sky PA shown in Gemini Commander.
  2. Slew to some point in the sky that’s good for sync’ing and do a solve and sync in SGP.

Now SGP knows that the current position of the Gemini corresponds to the sky PA reported by the plate solve. SGP also knows how to “map” the rotator’s internal position angle to the camera’s sky position angle. DO NOT attempt to do anything in Gemini Commander other than to enable / disable temperature compensation after you have done the solve and sync.

A note – home position for the Gemini is 0 degrees instrumental position angle. However, that is not where the cord wrap sensor is located. The sensor is located at 75 degrees instrumental position angle. So, when you do a home, Gemini first goes to the sensor; reverses and goes to the home position (0 degrees). If you connect SGP to the Gemini right after a homing, SGP shows the rotator at 0 degrees. That’s why a solve and sync is needed to tell SGP that 0 degrees instrumental corresponds to X degrees on the sky.

If you use PHD2, make sure you connect it to the Gemini so it can tell when the Gemini is moved (ie, rotating during a meridian flip).

I also use the AP ASCOM interface for my mount – the Gemini does not need to know anything about your mount.

Charlie

This sounds very helpful and may indicate why my rotator has a mind of its own,

many thanks

JK

Connecting the rotator in PhD and reversing the direction in the Gemini driver did the trick.

Session worked as it should tonight.

Jk