#M81 M82

78 messages · Page 1 of 1 (latest)

raw fern
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so far i've spent this year ghatering data for IC 405 but it's too late for it now so i thought i would take on something nice and bright to finnaly get some results, so i did, i have one night worth of data 102 frames 5min each summing up to 8.5h i was expecting a really nice image and i thing my data is pretty good but i just can't manage the supper bright M82 and the core of M81, also i can't bring out any colour out of it i mean i can but it comes out only in the brightest parts

here is a stack of 91 frames
https://drive.google.com/file/d/19lx65z26d4DDNIUAh5edkzWWEih9NAHP/view?usp=sharing

for some reason my flat frames didn't work but it's managable

Google Docs
91f.stack.tif
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here it looks like the core of m81 is overexposed but histogram doesn't show that it is

image.png
unreal burrow
raw fern
# unreal burrow wow

that's what i was aiming for but the colour only showed up in the brightest parts,can you walk me through what you did?

unreal burrow
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That's almost all I did

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Like that was not a difficult data to get good results so I didn't do much things

raw fern
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im gonna do some colour adjustments and fine tune the streatch

raw fern
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also i just went with the M81, M82 doesn't really look like anything here so just cropped out

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im done
i was really hoping for more detail but i guess my guiding/seeing limits me in what i can resolve
@unreal burrow

91f.drzl2x.recomp.maskstreatch.png
unreal burrow
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Well the image definitely needs a denoise in the galaxy

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But I think an blurX could help with the details

proud vapor
proud vapor
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the color is there, tricky to get out (for me at least). the core and the stars seem to be over exposed. maybe the subs were too long or your offset is not right. 🤷‍♂️

raw fern
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that's what the histogram looked like

image.png
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so from my understanding all tha data was in this spike, and since the spike is not toutching the right wall there are no over exposed pixels

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(that's just a representatuon in paint)

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here is a histogram of a single exposure from siril

image.png
proud vapor
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this is the window/section you want to watch in NINA when deciding how long to make your subsframes. It'll tell you how many pixels are saturated.

Screenshot_3.png
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This is from a flat frame, so ignore the histogram lol. The Max (2x) is showing 2 pixels that are saturated (over exposed). and it looks like 1x dead pixel.

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i'm almost certain those 5min subs at that iso is what blew out the core.

raw fern
proud vapor
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yeah

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the dead pixel thing was an error on my part

raw fern
proud vapor
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i have no idea. that histogram in siril is ideal, for the most part. is gimp showing it further to the right?

raw fern
proud vapor
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that is what i would expect from what you showed me

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i mean, the final stack

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can you share a single sub frame here?

raw fern
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yea i was expecting something like that too after having issues with procesing it

raw fern
proud vapor
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if i open it with my image viewer, it shows it clipped way to the right

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but!

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pixinsight shows it more realistically i suppose

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my siril isn't debayering it, might be why it's showing the histogram wrong there

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nope, that wasn't it 😅

raw fern
proud vapor
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nah it's ok, i didn't check the 'debayer' box when opening it

raw fern
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can i make like a negative offset? to take long exposures but not clip the data?

proud vapor
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if you're using a DSLR I don't know if you can even change the offset. maybe just the ISO. what bortle sky are you shooting in?

raw fern
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and im in B7

proud vapor
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light pollution is going to be a big problem with long exposure at that ISO. i'm in Bortle 6 and I had to keep my subs at 3min at iso 800 when I used my dslr

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it was a canon t7i

raw fern
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but it's not the sky that gets blown out its the stars, no matter the sky the stars stay the same brightness, only limit is how dimm stuff i can see bc if an object can't outshine the sky itself than i cant see it(unless using narrowband)

proud vapor
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you're camera is collecting the light pollution + the signal from the deep sky object. galaxy cores are bright already, if you add over exposed light pollution on top of that ....

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try a few subs at 180s and 120s to see the difference

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same iso*

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in NINA the histogram should be rather close to that first quarter on the left for each sub

raw fern
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i'll try shorter exposures but sadly i don't see any clear nights in the next 2weeks at least

proud vapor
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yeah 😦

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the other night i was out and just shooting Lum with my mono camera, with a ~70% moon, a 60s exposure was all i could get

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that was after lowering my normal offset of 25 down to 5 lol

raw fern
# proud vapor

see I don't understand , you have plenty of space between the spike an the right side of a histogram

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unless im reading something wrong

proud vapor
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you're reading it right but understanding it wrong

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you keep your histo to the left in subs, stretching it to the right to bring it out

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if you shoot with the histo on the right, stretching it over exposes things that are probably already over exposed

raw fern
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ooh you're right

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so i need to shoot exposures giving me a histogram detached from the left but with space for stratching on the right

proud vapor
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yes 🙂 don't want it clipped on the left either, with zero values for pixels

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here's a stacked result of some Ha data. look how far left the histo is. the top part is zoomed into the histo

Screenshot_7.png
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that gives me all this room to stretch to this result

Screenshot_8.png
raw fern
proud vapor
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no, that's a full stack of who knows how much data, a few hours i think

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here's a single exposure from my color camera

Screenshot_9.png
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forgot to use a debayerd one. unstretched and stretched subframe

Screenshot_10.png Screenshot_11.png
raw fern
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nice

proud vapor
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a 3min sub with those bright stars almost completely over exposed them. you can see the pixel values at the bottom

Screenshot_12.png
raw fern
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oh that's close heh