Hi,

I've been working out autofocus with my ZWO EAF + ZWO ASI183GT + TS 76EDPH scope but I am having some issues.

1. Algorithm: I have tried many combinations. Autoselect start and subframe works fast using SEP and iterative and works well while I am paying attention and manually start from a good rough focus but left alone during an automated sequence it fails. Full field seems to work better when left alone with a step of 25 if focus is close to correct but sometimes it goes off in the wrong direction, loses focus then fails to detect stars (because of going completely out of focus) and it aborts the sequence. Any suggestions as to what algorithm, initial step size, etc.?

2. While watching the curve it looks like the focuser moves further going back than going in. I suspect because the motor has to work against gravity. Will adding some steps to the backlash option help with this?

3. During a sequence the measured HFR with a 5% threshold triggers the autofocus every single frame captured. Should I increase the threshold or there is something else than I am missing? I would like for the autofocus to check every frame for focus but only trigger a focus routine when appropriate and not every time.

4. I have tried to determine an offset for each filter so that I only need to focus using the luminance filter but the values measured for the steps are different every time I run an autofocus sequence. Even for the same filter it will have a different reading every time I perform autofocus. So I can't establish a consistent offset. Is there any work around for this.

Thanks in advance for your help.

Read More...