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M45 - Seven Sisters (and extended relations) - C&C welcome

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#1 DivisionByZero

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Posted 05 December 2021 - 08:26 PM

I'm finally at the point where I feel some C&C can start pointing me to improvement areas. Perhaps ironically, this image is probably not deep enough, but I think it starts to exhibit the issues I could use some feedback on. Namely, the balance between stretching and noise reduction. Color is also a perennial question.

I've added a bit more luminance to the original pass at M45 (earlier revisions on A-bin). However, I ended up not allocating a lot of range and contrast to the outer regions and instead brought out the areas close to the stars. I didn't use as much NR as a consequence. It was inadvertent and I find myself torn about the outcomes. I could use some comments about it all. I don't like things that look overbaked, but actually understanding where that point is seems elusive to me right now.

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General comments and critique are welcome! Thanks for looking.
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#2 Ibuprofen200mg

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Posted 05 December 2021 - 11:32 PM

Nice image! It doesn't look overbaked to me. In terms of the color I think the saturation on the red stars is a bit too high. As for the noise level it doesn't detract from the image as is, but 2-4 more hours would probably show significant improvement. I would maybe try raising the black point just a little and see how it looks, currently the background is a little dark to my eye. As an aside, I'm guessing you removed the corrector from the focuser tube to get the 114 down to ~500mm FL? Interesting!


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#3 DivisionByZero

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Posted 06 December 2021 - 01:37 AM

Nice image! It doesn't look overbaked to me. In terms of the color I think the saturation on the red stars is a bit too high. As for the noise level it doesn't detract from the image as is, but 2-4 more hours would probably show significant improvement. I would maybe try raising the black point just a little and see how it looks, currently the background is a little dark to my eye. As an aside, I'm guessing you removed the corrector from the focuser tube to get the 114 down to ~500mm FL? Interesting!

Thanks for the comments.  I'll definitely take a closer look at the reds again and probably redo the stretches as well to get more of the distant nebulosity like in the earlier revisions.

 

Yes - if you're familiar with the "regular" Astromaster 114, it has a spherical primary and a Bird-Jones corrector.  My dad had found it at a garage sale and sent it to me, so I technically paid $0 for the OTA!  Several years ago I modified it for prime-focus imaging and moved a 114mm parabolic into it.  I used to know where the CN post was that described the changes since I hacked about 3" off the back-end to move the mirror cell up.  Some of my early Astrobin images are with that spherical primary.  Anyway, it's still the 1.25" draw-tube so I have no real way to put a commercial coma corrector into this scope.  The rig from a few years ago can be seen here.  The new equipment for today are an ASI1600, a filter wheel, and a Raspberry Pi that rides along.  All of those have been huge improvements over the mono-mod 20D I had been using.

 

I was thinking of a consequence of that little scope that's kind of clear in this image.  The vanes are really thick (like 2mm thick) and the aperture is only as big as it is.  I'm thinking that the PSF of the scope is enormous as a result and so I end up with those giant stars in my images!


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#4 matt_astro_tx

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Posted 06 December 2021 - 08:41 AM

So if I'm reading that right, this is basically a 30 minute exposure.  Impressive!  You'll need to add a few hours to really bring the background out.  See my 10 hour image (with an OSC) here.  10 hours is a bit overkill but M45 is my "filler" target while I wait for others to rise.  I'm thinking about pushing it to 20 to bring out the IFN.

 

As with anything more time = less stretching.


Edited by matt_astro_tx, 06 December 2021 - 08:42 AM.


#5 DivisionByZero

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Posted 06 December 2021 - 08:57 AM

Very nice, matt_astro_tx! The large integration really shows. This one here is 1hr 45m total. It's funny: I was using it as "filler" as well while I waited for M42 to rise which is why I only added 30 minutes over the first night's data. I agree it needs more integration to really bring the rest out.

#6 Ibuprofen200mg

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Posted 06 December 2021 - 09:15 AM

Thanks for the comments.  I'll definitely take a closer look at the reds again and probably redo the stretches as well to get more of the distant nebulosity like in the earlier revisions.

 

Yes - if you're familiar with the "regular" Astromaster 114, it has a spherical primary and a Bird-Jones corrector.  My dad had found it at a garage sale and sent it to me, so I technically paid $0 for the OTA!  Several years ago I modified it for prime-focus imaging and moved a 114mm parabolic into it.  I used to know where the CN post was that described the changes since I hacked about 3" off the back-end to move the mirror cell up.  Some of my early Astrobin images are with that spherical primary.  Anyway, it's still the 1.25" draw-tube so I have no real way to put a commercial coma corrector into this scope.  The rig from a few years ago can be seen here.  The new equipment for today are an ASI1600, a filter wheel, and a Raspberry Pi that rides along.  All of those have been huge improvements over the mono-mod 20D I had been using.

 

I was thinking of a consequence of that little scope that's kind of clear in this image.  The vanes are really thick (like 2mm thick) and the aperture is only as big as it is.  I'm thinking that the PSF of the scope is enormous as a result and so I end up with those giant stars in my images!

I really appreciate that sort of thing in this hobby, DIY approaches and working with what you've got. Yeah dropping $5k on the latest astrograph would be nice, but building something yourself is also very rewarding. 



#7 matt_astro_tx

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Posted 06 December 2021 - 09:54 AM

I really appreciate that sort of thing in this hobby, DIY approaches and working with what you've got. Yeah dropping $5k on the latest astrograph would be nice, but building something yourself is also very rewarding. 

I can't agree more.  While my primary imaging rig is all purchased hardware, my newtonian was a labor of love.  I'll never let go of that one, except to gift it to one of my sons one day...




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