SGP and Optec Gemini Focuser

Hello. We have SGP and an Optec Gemini Focuser. If anyone else has this setup, would you mind sharing your settings for auto focus? I cannot get SGP to reliably focus with this setup. As a result, I have to go out to Maxim which does a great job. Not having this ability in SGP is causing us to start looking for other imaging solutions. I really like SGP, but this current problem is preventing our moving forward.

Appreciate any help. Grady

I don’t have an Optec focuser but I’m sure it would help if you list what telescope and final focal length ( if using a reducer) and it wouldn’t hurt to list your camera.

Also, the help section has great instructions on how to get a good starting point. I was having troubles with one of my scopes but after reading that section, I found I was way off on the steps. I was trying around 300 steps but the calculations in the manual came back that I needed to be a little over 1,000. Steps.

Here’s a good reference for getting auto focus setup:

If you still have issues after going through that, then post some auto focus curves and a lot and I can probably get you going.


And a tip.
Don’t read it when you’re frustrated. I did and the last step in the calculations for getting a starting point, I read it as two steps. I could not come up with a valid reason why they wanted me to reduce the final step size by 1 step. But hey they are the smart ones so I did. :relaxed::joy:


I have an Optec Gemini that I use on two scopes: 130mm APO with a 780mm fl and a 12" Meade ACF with a 1830mm fl. If you are new to the Gemini, you may not realize how small the steps are (0.11 micron!). This means you need a lot of steps to get a usable change in HFR between focusing frames. You also need to avoid getting stars that are donuts, when using a catadioptric system.

That said, I use 9 focusing frames with the focuser moving 1600 steps between frames. Your goal is to have the worst focus frame have an HFR about 3x that of the best focus frame. Use the resulting focus graph to analyze the results of a focusing run and adjust from there.

It can be useful to do a manual focus run to get something close to a good focus before running the auto focus routine. SGPro’s philosophy is to maintain a good focus during the imaging run but not to take any out of focus image and get a good focus. If you already own FocusMax, one option is to use it to get your initial focus before turning things over to SGPro.

However, I have found that when properly configured, SGPro and Gemini produce excellent auto focus results without having to resort to an external focusing solution like FocusMax.


I have three Optec DirectSync focusers. All three work perfectly with SGP. I use 7 focusing frames with 600 steps per frame. I set for 2x2 binning and 8 second exposure. I always use Frame and Focus first to get the focus ‘close’.

Hey all. Thanks for the feedback. Will try these points and see what we get. Thanks.

If you’re still looking for input…

I have a couple Gemini’s and focus with 7 data points and a step size of 1500.
One trick is to set the focuser to the mid-point of 57,600 steps on a “typical” day, then focus using the scope’s built in focuser, e.g., the focus knob on an SCT. Doing this will eliminate the possibility of hitting the 0 or 115,200 step mark while focusing on really cold or really hot days.

And as @chasmiller46 said, the Gemini has a LOT of steps.