John replied to the topic 'Linear 1 Pass focussing problem' in the forum. 3 months ago


Answers below…

When you have varying amount of cloud during the focusing exposures, does the algorithm in some way compensate for this or do we expect the points to be scattered further from the best fit curve? When I say compensate, are the hfr values adjusted to a mean sky background using photometric methods? In short can we expect focusing to work during the passage of high cloud (when varying but sufficient stars detected)?

Generally cloud will cause problems. Although SEP background subtracts object flux as part of its processing you will unreliable results when it’s cloudy.

Turn guiding off whilst focusing in the focusing module doesn't work. I watched the clouds pass by in the guiding module whilst focusing was happening but guiding continued. Without testing I am not sure I want to turn guiding off anyway but none the less it should work?

The idea is that if you have a separate guide scope then no need to turn guiding off. If you have an OAG then it will move out of focus and potentially cause guiding issues, hence the option to suspend guiding. The option checks that the imaging and guiding scopes that you setup in Ekos are the same. If not, it will not suspend guiding, even if option checked.

During a passage of time when cloud prevents sufficient stars to be detected, focusing fails and focuser is put back to last known focused position, what happens next? Does the mount continue to track with image capture suspended? Does the focus module pause for a short while then attempt a further focus repeating focus attempts until either sky clears sufficiently for a successful focus or job end condition is reached.?

When focus fails it retries. On 3 fails it returns control. If you run focus from the GUI then you have control. If it’s running from the scheduler then the scheduler has control. It usually will just retry focus again.

Usually, when focus is running, tracking is running, capture is suspended and guiding may be suspended (see above).

Hope this helps.