Additional live-stacking filters

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calan
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Additional live-stacking filters

#1

Post by calan »

1. Add a filter based on the "roundness" of one or more reference stars. The brightness and FWHM filters are nice, but they have to be constantly adjusted to maintain the same quality of stars... i.e. FWHM can go up and brightness can go down for the same <relatively speaking> quality of stars, as time goes by,

2. Add an inverse filter for sky brightness. If average sky brightness goes above a specified threshold, no stacking

3. Add a shut-off time for live stacking. I may want to start stacking at midnight, and have it automatically stop stacking at 5:00am, for a number of reasons.
Last edited by calan on Tue Aug 09, 2022 12:48 am, edited 1 time in total.
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admin
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Re: Additional live-stacking filters

#2

Post by admin »

Hi,

Idea 1 is already on the list of potential features to be added in future.

2 is interesting - I hadn't considered that before, but it makes sense to try to catch thin cloud or the target dropping into the murk nearer the horizon.

3 is something that you can achieve currently using the sequence - set it up to start live stacking and then wait until 5:00 (or astronomical dawn, or whatever), then stop live stacking. I think I would probably not worry about putting a separate implementation into live stacking because the sequencer is designed to be the tool for people to use when they want to put together that sort of complicated use case.

The interesting part with 1 and 2 is how to design them into the UI - having 2 filter tabs for brightness and FWHM is fine, but having 4 would be excessive. I might have to have a single 'Frame filtering' tab with subdivisions inside it?

cheers,

Robin
calan
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Re: Additional live-stacking filters

#3

Post by calan »

admin wrote: Sat Aug 06, 2022 1:28 pm 2 is interesting - I hadn't considered that before, but it makes sense to try to catch thin cloud or the target dropping into the murk nearer the horizon.
Yeah, I would use this feature all the time. Neighbor's lights come on in hazy skies, fall asleep before dawn and a stack gets ruined because of sunrise, clouds or haze roll in, etc.
admin wrote: Sat Aug 06, 2022 1:28 pm 3 is something that you can achieve currently using the sequence - set it up to start live stacking and then wait until 5:00 (or astronomical dawn, or whatever), then stop live stacking. I think I would probably not worry about putting a separate implementation into live stacking because the sequencer is designed to be the tool for people to use when they want to put together that sort of complicated use case.
Interesting. I haven't played with the sequencer, mostly because I've always thought of it as doing many automated things...and I always seem to need (or want) to babysit my rig while stacking. :)
admin wrote: Sat Aug 06, 2022 1:28 pm The interesting part with 1 and 2 is how to design them into the UI - having 2 filter tabs for brightness and FWHM is fine, but having 4 would be excessive. I might have to have a single 'Frame filtering' tab with subdivisions inside it?
Hmmm. Well for starters, you could combine the brightness and FWHM into one tab, with them next to each other. You could make the FWHM bars narrower (and fewer of them), and I don't think we need to see that many brightness blips...or at least I haven't.

On a related note with brightness and FWHM:

How about adding an "auto" function to the FWHM filter, similar to the one for brightness? As mentioned above, I'm always having to nudge the FWHM upwards as time goes on...it would be nice if SC could automate that somehow. Like, x number of frames within some small percentage of each other, and the threshold changes?

And, maybe add parameters that let us set the number of measurements to average for both? I admit that I have no idea how the auto function currently works for brightness, but it would be nice to have some control on how many frames get dropped before the threshold adjusts, and how many good frames get captured once recovered before averaging starts again. Just thinking off the top of my head and mostly babbling. It's been a long night. :)

Keep up the excellent work!
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Re: Additional live-stacking filters

#4

Post by admin »

Hi,

do you have any idea why you need to nudge the FWHM upwards? Could it be that your focus is drifting slightly (maybe as the temperature changes). I'm kind of worried that this is the sort of thing that someone else will be relying on the FWHM to detect...

cheers,

Robin
calan
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Re: Additional live-stacking filters

#5

Post by calan »

admin wrote: Sun Aug 07, 2022 1:47 pm Hi,

do you have any idea why you need to nudge the FWHM upwards? Could it be that your focus is drifting slightly (maybe as the temperature changes). I'm kind of worried that this is the sort of thing that someone else will be relying on the FWHM to detect...

cheers,

Robin
I'm really not sure. I haven't been able to notice any significant change in focus (batinov mask) when I've checked, but I don't check it often.

My guess is that it's the scope tracking through different sky conditions. I usually start just as objects cross the meridian, as the OKC light dome pretty much rules out imaging to the east/south-east (and I don't want to deal with a meridian flip, especially after just 30 minutes into stacking). So, I've got the best skies I'm going to get when I first start stacking, and then as the scope tracks west and into lower altitudes, the FWHM drifts. So I bump it up to keep stacking at the same quality of star shapes (setting the threshold right at the average tops of the good bars).

I constantly battle wind gusts, so without the "roundness" filter, the FWHM filter is a lifesaver. I just have to watch it and adjust it periodically.
Last edited by calan on Sun Aug 07, 2022 2:03 pm, edited 1 time in total.
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Re: Additional live-stacking filters

#6

Post by admin »

Hi,

ok, thanks, that makes sense, and it makes a good case for roundness being useful in different situations to FWHM.

cheers,

Robin
calan
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Re: Additional live-stacking filters

#7

Post by calan »

Yeah, I think the roundness and inverse sky brightness filters would really round things out for those of us in windy, variable, and light poluted conditions.
givoly
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Re: Additional live-stacking filters

#8

Post by givoly »

calan wrote: Sun Aug 07, 2022 2:06 pm Yeah, I think the roundness and inverse sky brightness filters would really round things out for those of us in windy, variable, and light poluted conditions.
Robin - the brightness filter needs both upper and lower limits - to filter frames above or below a set value. In dark skies, clouds are dark - and the filter as is might work for them. However, in Bortle 7-9 skies, the clouds often lighten the skies and raise brightness... and one would want to filter out those frames. I cannot use the brightness filter because of this. Inversing it is actually not the right solution, IMHO. You really want to filter higher or lower brightness than the established range for the image. Variation in brightness in either direction mean that what you're capturing is no longer what you had intended to capture, at least in most situations.

Looking forward to the addition of a max value :) Thanks for the amazing evolution of the app!
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Re: Additional live-stacking filters

#9

Post by admin »

Hi,

that's odd - I wasn't expecting that to happen... The brightness filter measures the star brightnesses rather than the overall brightness, so the thin cloud would almost certainly dim the stars more than it adds to the background in the region of the stars.

I wonder if the issue is that with the cloud arriving the fainter stars are lost, meaning that the average brightness of the stars being detected goes up (even though the stars themselves are a bit dimmer).

Will have to think about that - some way to track the stars so that if some are lost we still count them as contributing zero to an average might do the trick...

cheers,

Robin
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