When using FWHM multistar focusing I find that usually the focus is best at the very centre of the frame and not so good at the edges.
Sometimes, when using optics that exhibit field curvature, it is best to have the best focus point away from the middle of the frame so that the edges maintain better quality (at the expense of slightly reduced quality in the frame centre).
The current FWHM multistar focusing routine minimises the average FWHM score. Would it be possible to add an option so that focusing position is based on minimisation of the mean average deviation from the median fwhm value? This would optimise focus quality across the whole frame.
Andy
Additional option for FWHM multistar focusing
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'+1' posts are welcome in this area of the forums to indicate your support for a particular feature suggestion. Suggestions that get the most +1's will be seriously considered for inclusion in future versions of SharpCap.
'+1' posts are welcome in this area of the forums to indicate your support for a particular feature suggestion. Suggestions that get the most +1's will be seriously considered for inclusion in future versions of SharpCap.
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Re: Additional option for FWHM multistar focusing
Hi Andy,
I see what you are getting at, and in theory we could do all sorts of calculations on the star FWHM data and feed them into the system in place of the current FWHM average. However, the issue is working out whether such a setup would give a clear, strong signal that SharpCap can use to home in on. One of the key challenges of building the autofocus in SharpCap is working out ways to tell the difference between a real minimum in the focus graph that indicates best focus and some sort of random dip that is just the result of fluctiations in the data.
In this case, I even wonder if the suggested measurement might be at a maximum when in best focus - when you are significantly out of focus then all the stars will be large fuzzy blobs and the difference made by center vs edge would probably be minimal. I think it's not clear and would have to be tested to see how the distribution of FWHM varies with distance from best focus for a suitable type of telescope.
Surely a simpler approach would be to enable the area selection tool in the toolbar and use an area of the image about half way to the edge to perform measurements when focusing.
cheers,
Robin
I see what you are getting at, and in theory we could do all sorts of calculations on the star FWHM data and feed them into the system in place of the current FWHM average. However, the issue is working out whether such a setup would give a clear, strong signal that SharpCap can use to home in on. One of the key challenges of building the autofocus in SharpCap is working out ways to tell the difference between a real minimum in the focus graph that indicates best focus and some sort of random dip that is just the result of fluctiations in the data.
In this case, I even wonder if the suggested measurement might be at a maximum when in best focus - when you are significantly out of focus then all the stars will be large fuzzy blobs and the difference made by center vs edge would probably be minimal. I think it's not clear and would have to be tested to see how the distribution of FWHM varies with distance from best focus for a suitable type of telescope.
Surely a simpler approach would be to enable the area selection tool in the toolbar and use an area of the image about half way to the edge to perform measurements when focusing.
cheers,
Robin