Auto focus starting point


#1

I have found focus to be one of my weak points and have decided that only auto focus can save my sequences. However all of my attempts at auto focus have resulted in worse focus than when I started. I am looking for some suggestions for what values to use for fine and course focus steps in the Frame & Focus dialog.
My OTA is a TV NP101is at 540 mm FL with a Moonlite DRO focuser. Total step range is 0 to 12500 if I recall correctly. I read somewhere that a single step is 4.1 microns. The math tells me that this is either approximately half a meter of focus travel or 5 centimeters depending where I put the decimal point, both terribly wrong. I believe the Moomlite DRO has 3 inches (76.2 MM) of travel. If it does have 12500 steps then each step would be really small.

Bottom line, anyone have a suggestion where I should begin. I have tried 40 for fine and 500 for coarse but the auto focus routines have not been successful.

Anyone using a TV NP with a Moonlite focuser?

Thanks in advance,

Frank
37 N - 121 W


#2

4.1 microns is about right for the Moonlite focuser, this gives 50mm for 12500 steps and that’s not that far out. 18500 steps would give about 3 inches.

You need to experiment to see what the range is. My Moonlite focusers are smaller and only have a range of about 6200 steps.


#3

I don’t worry about the steps anymore. I worry about covering a range of HFR 3 to 3 on each side of focus. I want at least 9 data points so I find how much that total distance is (about 450 for my system, moonlight/Ed80) and set my move to that number. I make sure she is roughly in focus and let SGP do its thing.

As soon as I started doing this at Ken/Jared’s suggestion, I had no issues with focusing.

Good luck!
Chris


www.mainsequencesoftware.com