FWHM Filter

[SteveSD]

I'm not clear what the proper setting for the slider in the FWHM filter is. I believe I read in the manual that lower numbers are better but I don't know whether that referred to the proper setting of the slider control or whether that referred to lower numbers on the bars in the graph or both. Bottom line - about the only thing I understand about that filter is that the bars in the graph should come in green and that factors such as focus and star detection influence that. But I don't know what influence the slider has on that, where the slider should be set, and what other parameters are relevant to that filter.

Thanks in advance for your help !!

[admin]

Hi,

lower FWHM means that your stars are sharper (better focus, clearer seeing, etc). The idea of FWHM filter is to exclude frames from the stack that are of lower quality (higher FWHM) to improve the stack. Basically, set the level so that most frames (90%+) have an FWHM lower than the set value and therefore get included in the stack and a small fraction have a higher value and get excluded.

If conditions deteriorate (thin cloud, worse seeing, etc) then the FWHM will increase - hopefully past the level you have set - and the lower quality frames will be ignored.

As you can see, there is no single 'correct value' for this - it depends on your equipment and the conditions.

cheers,

Robin

[SteveSD]

Thanks for that !

Cheers back atchya !