Choosing best frames for integration, signal/noise, full-width-half-maximum

Here's an answer from Mabula I found on the forum;

The quality scores are relative. There is no absolute score to indicate what a good score is actually.

The score is calculated with a special formula that consists of star density, noise and star shape.

Simply said, star density and star shape are relative in terms of imaging scale in pixels. If you register frames of different image scales, this will become clear.

In relative terms, frames with stars with a large FWHM value  in pixels will get a low score. But it does not mean that the frames are bad, it could simply mean that you are shooting with a very long focal lenght.

Thanks Vincent! I actually saw that response linked beneath my query as a related topic -- AFTER I posted it. I'll try to pay a little more attention next time.

It will take a little more thought to use the score, rather than some arbitrary FWHM,  eccentricity number, or combination thereof. After all I don't care all that much about what percent I'm rejecting, I care about the quality of the frames. If I have a good, consistent night I might want 95% of them; a consistently bad night, perhaps 10%, and an inconsistent night maybe 50%. But perhaps I can suss that out by playing with the slider and seeing what frame-scores stay selected.

If there's an APP best practice for this, I'm all ears, as Ross Perot said.

Thanks again!

Thanks again!

You're welcome. 🙂 As for the best practice, it comes down to personal preference a bit I think and some experimentation. I usually never look at the frames anymore (blinking through them) as I know my rig is very stable now and things like aircraft trails aren't a big issue at my location. I tend to always go for about 95% to stack, with quality as the selected method and it always works very nice. If you, however, are in an area with loads of aircraft or other disturbances, it might be better to first do a pass through the frames before going this route. If a particular session makes you want to throw the slider down to 10%... I, personally, would just call it a day and go for the next. 😉 Satellite trails usually aren't a problem when you take enough subs.

Sigh. I could only dream of a "very stable" rig, I'm afraid. I'm culling frames due to eccentricity, or even jagged trails from time to time when there's some kind of hiccup. That sort of thing shows of nicely in lower-level stats, I'll have to throw some of my special brand of horror frames at APP and check out how it scores them.

Ow, sorry for that. Well those type of frames should be dealt with properly in APP using the quality method.

@rickwayne Where do you do this? Been using APP 4 years and dint know that was possible.

I believe they are discussing the "Lights to stack" slider in the Integrate tab.

@jhart Thanks will have a look for that.

Now if the slider were sensitive to how you've sorted the frames in the files pane (e.g., by eccentricity instead of quality for a specific dataset) that would be HUGELY useful. Have to see if it does indeed work that way. I've been sorting through the frames one by one and eliminating outliers manually, but the slider might be a nice, quick alternative. I'd probably still look at the dividing frame though.