WIP, my first M101, featuring Holmberg IV

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Mike in Rancho
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Re: WIP, my first M101, featuring Holmberg IV

Post by Mike in Rancho »

Thanks Ivo. :bow-yellow:

I think just to feel better about myself, I'll stack the SN hour in with the prior data. That way I'm just replacing things (supernovae, spaceships running away full throttle) removed by sigma rejection. ;)

I'll slowly get my head around NewSVD with time, feeling out how it reacts to different datasets and processing. I do most of my adjustments within SVD to the best I can manage right now, so any subsequent artifact repair is minimized.

One of the first things I did with PI was to turn off cosmetic correction for stacking, but yes it is likely the bigger stars have some full white pixels in there. My L subs are only 30s, but even on 10s tests I can saturate a few pixels of mere run-of-the-mill stars. Why these cameras don't have an SD card slot for expanding the full well I just don't know. :lol:

Most of my data here, despite being over two (soon three) nights, came in with very similar statistics, so they shouldn't be "too" funky. But I appreciate the explanation of what SVD might be turning up in data mining my stars. Makes me wonder if I have any program that could give me a graphic representation of a chosen star's PSF (like a 2D slice). :think:

Indeed for the weak 1-hour SN stack, I did back off sampled iterations to 5, which helped as to both ringing and noise amplification, but still otherwise was improved over pre-SVD.

Interestingly, the sample screen offered me the SN as a clickable starfishy. Query - is it really a point source anymore, or just little pieces strewn out all over? Billions and billions of pieces. :D
Mike in Rancho
Posts: 1154
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: WIP, my first M101, featuring Holmberg IV

Post by Mike in Rancho »

I threw my extra hour that has the SN into the whole pot for an 8-hour stack. :D

Bizarrely, to me anyway, rejection and averaging did not wipe out the SN, despite the 7:1 ratio. However, the color was all wrong, showing up in orange rather than the correct blue-white. Well, at least I had something to confirm location when blending it in! (the separate SN stacks were registered of course).

However, that oddball remnant of red-white SN prevented use of lighten mode for layer blending. So I had to use normal blend with a careful SN mask and 2 pixels of fuzz, and then I ran a second instance of layer but using color of Fg. That little two-step seems to have done the trick.

For my limited data I'm not sure I can do much else. Will probably upload the full field to a-bin later. For now though I just put together a side-by-side of similarly processed 7-hours from before the SN, and 8-hours which includes the SN but is also mask blended.

M101 SN side by side 2K.jpg
M101 SN side by side 2K.jpg (479.85 KiB) Viewed 1175 times
Mike in Rancho
Posts: 1154
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: WIP, my first M101, featuring Holmberg IV

Post by Mike in Rancho »

Here's a full field biggie res link to astrobin of my last processing. I think, SN and all, I'm a bit worn out on M101 so this might be the final.

But, anything anyone sees that needs fixing or a re-do?

https://astrob.in/evk4wv/0/
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Re: WIP, my first M101, featuring Holmberg IV

Post by admin »

The SN is the cherry-on-top for your visit of M101. :thumbsup: It's an area that's definitely worth revisiting if you ever end up going higher magnification and narrower fields.
Ivo Jager
StarTools creator and astronomy enthusiast
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