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Same Telescope, Same Camera, Same Mount, Same Filter--But very different results

Acquisition Deep Sky M101 Messier Objects Galaxy
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Jerry Gerber avatar
Jerry Gerber avatar
A week or so ago I shot this image using an Esprit 100ED, AM5 mount 2600MC camera and an L-Pro filter.  I'm happy with the results  (M3).

But last night I went out to shoot M101 and planned on shooting 5 hours but only got to 3 as the clouds moved in.  I do not like the results, it seems out of focus even though I was very careful in my focusing.  Until the clouds rolled in, my guiding was around or below .45". 

Could bad seeing be the reason the photo lacks that "wow!" factor?  Not enough subs?  something else..  I know it's definitely not one of my good images, but I don't know why...


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Jared Willson avatar
Jared Willson avatar
Seeing could certainly be a factor, but I suspect the bigger difference is in processing. Globulars have very high surface brightness, so they tend not to need very aggressive stretching. Galaxies usually have much lower surface brightness so need more aggressive stretching. With stretching you get more bloated stars and more noise. If you apply noise reduction, that tends to erode detail also, and you are more likely to need noise reduction with heavier stretching. So, more stretching and more noise reduction result in softer images with more bloated stars.
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Jerry Gerber avatar
Jerry Gerber avatar
Jared Willson:
Seeing could certainly be a factor, but I suspect the bigger difference is in processing. Globulars have very high surface brightness, so they tend not to need very aggressive stretching. Galaxies usually have much lower surface brightness so need more aggressive stretching. With stretching you get more bloated stars and more noise. If you apply noise reduction, that tends to erode detail also, and you are more likely to need noise reduction with heavier stretching. So, more stretching and more noise reduction result in softer images with more bloated stars.

Hi Jared,

I  think you are probably right.   I'm reprocessing it and am noticing exactly what you wrote, that over-stretching is bloating the stars and adding more noise.  I am guessing the best solution is to get 8-10 hours of integration time.   Thank you!

Jerry
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Brian Puhl avatar
Brian Puhl avatar
As someone that just picked up a color IMX571, I can tell ya unless you're a really low bortle scale, 4 hours isn't likely enough for M101.   Green signal will be strong, but red and blue will be very weak still.  I capped mine at 8 hours due to other issues but it still wasnt really enough and I'm bortle 4. 

Globs are bright, won't take long at all.
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Jerry Gerber avatar
Jerry Gerber avatar
As someone that just picked up a color IMX571, I can tell ya unless you're a really low bortle scale, 4 hours isn't likely enough for M101.   Green signal will be strong, but red and blue will be very weak still.  I capped mine at 8 hours due to other issues but it still wasnt really enough and I'm bortle 4. 

Globs are bright, won't take long at all.

Yeah, I am coming to the same conclusion.  I'm in Bortle 7 skies.  My plan was to shoot 10 hours of data, 5 hours, two nights in a row.  But during the first night, clouds rolled in after 3 hours--so much for plans.  Reminds me of the saying, "Man plans, God laughs".
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Tom Marsala avatar
Tom Marsala avatar
Yeah,I'm in bortle seven and I think I need at least 20 hours on my m 51.  Even six hours isn't enough anymore…
Tareq Abdulla avatar
Tareq Abdulla avatar
Tom Marsala:
Yeah,I'm in bortle seven and I think I need at least 20 hours on my m 51.  Even six hours isn't enough anymore...

Oh no, you killed my hope completely, i can manage like 2-3 hours for 2 nights, no more, saying you need like 10 hours or 20 and more, i feel like i will never make it right then, unless i buy like 3-4 telescopes of same to do it which is impossible for me, or having that a bit fast scope so i can collect light more, but i don't know even with fast how long i need under Bortle eight or nine anyway.
Tom Marsala avatar
Tom Marsala avatar
Oh no! Sorry!  I didn't mean you were hopeless!  20 hours will help my signal significantly.  But you can still get a great shot in under that for sure!  Do what you can with what you have-that's always my mantra.

I am still working on mine so we'll see if I ever get to 20, haha!
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Tareq Abdulla avatar
Tareq Abdulla avatar
Tom Marsala:
Oh no! Sorry!  I didn't mean you were hopeless!  20 hours will help my signal significantly.  But you can still get a great shot in under that for sure!  Do what you can with what you have-that's always my mantra.

I am still working on mine so we'll see if I ever get to 20, haha!

In all cases i will try by best hard if i can copy my setup, already have multiple camera, maybe add one more then i am done with cameras and move to scopes, if i can have like three scopes of each then 20 hours in shorter times or say few nights will be a piece of cake as long the sky is clear and conditions too.
TSquasar avatar
TSquasar avatar
I hear you Jerry, when it comes to integration time. Some of the most impressive photos on Astrobin have had 20, 30, or more hours. I just do not have the clear skies, at a good time, to record so much.
But here is an 1hr 49min of integration with M101.. 


M101 1hr 40
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