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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 04 March 2024 - 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 04 March 2024 - 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.



#30 _.lightworks._

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Posted 04 March 2024 - 10:12 PM

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.


I believe the problem is underexposure. At 1", F5.6 at 300mm, there are not a lot of visible stars even at 6400ISO. I feel like there are not a lot of bright stars in the region. I am positive I didn't mess up focus, because I could clearly see Jupiter's moons.

I guess I'll move on to widefield shots. Any recommendations for constellations that have some bright areas that'd be visible with around 45' of integration? (Other than Orion of course)

#31 EPinNC

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Posted 05 March 2024 - 09:03 AM

I believe the problem is underexposure. At 1", F5.6 at 300mm, there are not a lot of visible stars even at 6400ISO. I feel like there are not a lot of bright stars in the region. I am positive I didn't mess up focus, because I could clearly see Jupiter's moons.

I guess I'll move on to widefield shots. Any recommendations for constellations that have some bright areas that'd be visible with around 45' of integration? (Other than Orion of course)

Underexposure for sure.  One could argue that is the central problem in astrophotography lol.gif  We're trying to take photographs of extremely dim objects.

 

Depending on where you are, and if you have a decent view of the western sky, you might try the Double Cluster.  Here's mine with only 135 x 1.0s exposures:

 

https://www.cloudyni...ter-in-perseus/

 

If I still had the original data, I might be able pull a bit more out of it with better processing.

 

Messier 35, Messier 44, and Messier 67 might be decent targets as well.  These are all open clusters and are relatively easy.  Stars are very high-contrast subjects, so clusters can be imaged without much trouble.  (And getting good cluster images can be a challenge in itself!)

 

If you have decent view to the southeast, maybe try Messier 46 and 47 in the same frame.  Two clusters apparently close to each other.  M46 even includes a small planetary nebula.

 

Messier 81 and 82 are galaxies in Ursa Major, although it may be difficult to get any real detail.  You'll probably see a little something from them, at least.

 

Everything is good practice, even if it doesn't turn out as well as you hoped!  And really, when you just think about what you're trying to do, it's astounding that you can actually photograph these faint, distant things!  It's a mind-expanding experience.




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