Didge Posted November 10, 2022 Share Posted November 10, 2022 Hi, I use AP a lot for astrophotography stacking. The 'Select Best Light Frames' seems to work most of the time, but fails horribly at other times. This extract from the User Guide ... Quality is determined by the presence of artefacts such as star trails and periodic errors. is not very enlightening. How does it work - what are the thresholds - how does it distinguish between star trails and satellites for example ? More importantly, star trails or periodic errors aren't usually the important thing - particularly with modern guided mounts with low PE. Much more important is FWHM. I don't always want to chuck out x% of my frames, just because other frames are better. What I what to do is select all frames with a FWHM < 3" or some other number, depending on the seeing conditions when the images were captured. Can you add a feature for the user to select frames based on FWHM - similar to the way SiriL does ? That would be very nice Gary Quote Link to comment Share on other sites More sharing options...
Staff NathanC Posted November 25, 2022 Staff Share Posted November 25, 2022 Hi @Gary.JONES, This feature isn't something I'd be able to advise directly on how it functions, so I've raised it with the product experts internally and I'll get back to you. 🙂 Quote Link to comment Share on other sites More sharing options...
Didge Posted December 17, 2022 Author Share Posted December 17, 2022 Hi Nathan, Still hoping for a response on this Gary Quote Link to comment Share on other sites More sharing options...
Staff James Ritson Posted December 19, 2022 Staff Share Posted December 19, 2022 Hi @Gary.JONES, the procedure for selecting the best light frames is based on the quality of the 40 best stars found in each sub, where a good star is bright relative to the noise level, round, sufficient size (but not too big) with peaks in the middle. The help documentation may need updating as I don't believe that information is completely accurate... Quote Product Expert (Affinity Photo) & Product Expert Team Leader @JamesR_Affinity for tutorial sneak peeks and more Official Affinity Photo tutorials Link to comment Share on other sites More sharing options...
Didge Posted December 20, 2022 Author Share Posted December 20, 2022 Hi James, Many thanks for that info ... The problem with the AP 'best frames' function is that it is not based on a standard Astronomy metric - eg FWHM. When using the 'select best frames' function, entering a % is essentially a commitment to trash 1-x frames, regardless of how good they are. What would be better is to set a quality threshold - eg select frames with a FWHM <= X. Selecting 'big' stars increases the risk of selecting saturated stars, which leads to an unreliable assessment of image quality, because the brightness profile tends to be that of a truncated cone, rather than Gaussian. It's important to bear in mind that images are usually cropped - what is rubbish in one part of the image doesn't necessarily mean that the entire image is rubbish. What astrophotographers would *love* is for APh to generate a chart displaying the average FWHM for each frame - then the user could select which frames to keep/discard, based on the FWHM and visual inspection - which is necessary to avoid frames being inappropriately discarded because of saturated stars or other artefacts that do not affect the quality of the part of an image containing the target. I hope that makes sense Regards, Gary Quote Link to comment Share on other sites More sharing options...
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