SharpCap Forums

Hi Robin,
a star roundness filter would be very good.
I shoot with a 16" dobsonian on a platform or a Samyang 135mm on a printed table at times up to 40s.
I don't point. The filter wouldn't save "taken" exposures.

https://www.astro-forum.cz/viewtopic.ph ... 2&start=30

Best regards

Tomáš/Aquarius

Hi,

yes, that would be nice - I did look at it once before and struggled to get a reliable measurement of the roundness (which is obviously a requirement for being able to filter on it). Would be worth another look though.

cheers,

Robin

Hi Robin,
an algorithm that could be used to track the roundness of stars is already in Live Stacking. There is a good chance that Frame To Frame Offset could be used. If the offset between images exceeded the specified limit at any point in the image, the image would not be saved.
Best regards
Tomáš

Hi,

I think that's a tricky one actually - it would work if all the relative movements were happening steadily, but we know that they don't do that. You could imagine a situation like this...

Frame 1: Steady all through
Frame 2: Steady for 75% of frame, then drifts between 75% and 90% complete - enough that we would worry about trailing stars
Frame 3: Steady all through

Frame 2 would show no offset from frame 1, since the initial 75% being good would be enough to put the detected stars pretty much at the same positions as in frame 1.

Frame 3 would show an offset from frame 2, but has no drift in it.

Here we would wrongly reject frame 3 and keep frame 2 based on just the offset from one frame to the next

cheers,

Robin

Hi Robin,
thanks for your reply. I will test how the relative motions of the stars between images correlate with the stretching of the stars.
Best regards
Tomáš