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Untracked astrophotography targets

Astrophotography Beginner DSLR DSO
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#26 EPinNC

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Posted 28 February 2024 - 06:59 PM

Pardon me for reviving a thread that I probably should have let to rest. I need some advice again.

Is the M33 possible untracked at any of the focal lengths I mentioned earlier? [300*1.6=480mm {F4} (1" per sub) and 75*1.6=120mm {F5.6} (2.5" per sub)]

I searched up for untracked shots, and most of them were taken at 135mm at 1.5" per sub.
I will be content with just about being able to see the arms of the galaxy.

Do you guys have any suggestions?

Thank you.

While M33 is a relatively large target, it has very, very low brightness.  It's a tough one.  There is nothing stopping you from trying, though!  I tried it 3 years ago under Bortle 7 skies, untracked (and with a bit of shutter vibration, too -- yay!), a zoom lens at 140mm, ISO 3200 and 180 exposures at 1.0 second each:

 

r_pp_Messier-33-Triangulum-Galaxy-1.0s-f5.6-iso3200-140mm-180frames_stacked-as-gnr-bgr-cc.jpg

 

There's a slight hint of structure, but no clearly-defined arms.  Maybe if you took 1000 exposures, you could get a bit more out of it.

 

Give it a whirl and see what you come up with!



#27 _.lightworks._

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Posted 28 February 2024 - 09:04 PM

While M33 is a relatively large target, it has very, very low brightness. It's a tough one. There is nothing stopping you from trying, though! I tried it 3 years ago under Bortle 7 skies, untracked (and with a bit of shutter vibration, too -- yay!), a zoom lens at 140mm, ISO 3200 and 180 exposures at 1.0 second each:

r_pp_Messier-33-Triangulum-Galaxy-1.0s-f5.6-iso3200-140mm-180frames_stacked-as-gnr-bgr-cc.jpg

There's a slight hint of structure, but no clearly-defined arms. Maybe if you took 1000 exposures, you could get a bit more out of it.

Give it a whirl and see what you come up with!


This gives me some hope. If it is clear tonight, I'll give it a go. 300mm if I can get 1" without significant trailing, or whatever FF that gives me at least 2" without trailing.

Thanks!

#28 _.lightworks._

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Posted Today, 07:36 AM

I shot it. Neither DSS nor Siril could stack all 800 1" subs I took. Only a 400 subs version was possible, and the galactic core is just about visible with strong stretches.

#29 EPinNC

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Posted Today, 01:21 PM

I shot it. Neither DSS nor Siril could stack all 800 1" subs I took. Only a 400 subs version was possible, and the galactic core is just about visible with strong stretches.

I've never used DSS.  I have used Siril for several years.  The most I've thrown at it is 902 subs (Messier 76).  Producing that stack took a whole day on an old, slow computer.  But it worked.

 

What happened specifically that caused it to only stack 400?  If two different software packages are refusing to stack some images, then there's probably something odd about the particular images it doesn't want to stack.

 

Even if you can stack all of your subs, it's still only going to be 800 seconds, or 13.3 minutes.  That would probably show a bit of the galaxy, but you'd have to stretch it really, really hard to get anything more than a gray blob.

 

Again, M33 is a very difficult target because it's so diffuse.  Even my 4 hour integration, with tracked 30-second subs, doesn't really do it justice.  So, don't feel bad if you can't get much out of it.  As Bob would say, "the pretty pictures don't come easily."

 

Frankly I would turn my attention to more accessible targets.  You're really tackling a formidable foe with the equipment you have.




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