A couple of quick questions about autofocus with filter wheel

Hi Everyone,

I will start with my equipment:
QHY Filter Wheel 5 filters
MotoFocus Relative focuser but using ASCOM driver so SGP thinks is absolute focuser
WO Megrez 80mm Triplet with focal reducer (380mm)

1st Question: When focusing with narrow-band filters like OIII and Ha, I like to point the scope to a bright star near the object that I will imaging, perform the autofocusing and then point the scope to the area of sky that I really want to image. How do you tell SGP that the first target is focusing only? And the 2nd target is really imaging, so no need to focus or plate solve?

2nd Question: I have used the above setup with my QHY8L (OSC CCD) and SGP with no problems. SGP was able to autofocus with no issues and fantastic images. But when I tried to autofocus with my OIII filter last night, smartfocus was failing over and over. Then I disabled smartfocus and I noticed that it looked like it was just focusing in one direction and at the end of the focusing process, it was still out of focus. I know because I was manually focusing at the beginning and SGP was taking the image out of focus and call in it done. I’m attaching a couple of images, but I really don’t know why the points of data are in the zero axis and it can never achieve focus.

If you have any ideas about what could be wrong and any suggestions for changing the existing parameters, please let me know. Thanks for your help


We don’t really have this paradigm in SGP. Since our auto focus uses the entire image we recommend just focusing on target rather than finding a bright star (as SGP will use multiple stars no matter what…a single bright star won’t make a significant difference)

You’ll likely need to increase your exposure significantly for narrowband filters. We recommend setting up offsets for your filters and using the “Adjust focus per filter” option to apply these offsets and then focus with Lum.