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M45 Pleiades tips/suggestions

Astrophotography CMOS DSO Imaging
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#1 Plorimor

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Posted 10 December 2023 - 03:18 PM

Tomorrow looks like it will be a great night for me to get out and take another shot at imaging the Pleiades! I’ve attempted it once previously, and am wondering if anyone has any advice for me to use on my second attempt (besides more integration time haha)

Here’s my first attempt:
https://imgur.com/a/DEZSxmF

EvoGuide 50dx
ZWO asi183mc
UV IR cut filter
Star adventurer 2i
20x120s subs (guided)
15 darks
15 flats

Would a shorter or longer exposure time help at all? It seems like I’m getting done pretty strong halos around the main stars.

#2 WLR_DAD

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Posted 10 December 2023 - 03:32 PM

You are off to a great start.  As you mentioned, more integration time is needed.  Those are not halos around a the main stars, that is nebulosity.  You want more, not less of that.  


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#3 Plorimor

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Posted 10 December 2023 - 03:42 PM

You are off to a great start.  As you mentioned, more integration time is needed.  Those are not halos around a the main stars, that is nebulosity.  You want more, not less of that.  

That’s a good thing to have wrong on my end I guess! Glad to know I was able to pull a good amount of nebulously with only 40min



#4 Spaceman 56

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Posted 10 December 2023 - 03:44 PM

I would drop the 120 second exposure time down to 60 as a starting point. then shoot to or three times as many subs at least.

 

this would give the Star Adventurer a better chance to keep on track, and you should get tighter stars, with less bloat.

 

Maybe try and get 100 or so 60 second shots at least. another option would be 200 x 30 second shots.

 

I got this using 15 second subs, but I am Bortle 1.   

 

M45 Pleiades.

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#5 Plorimor

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Posted 10 December 2023 - 03:47 PM

I would drop the 120 second exposure time down to 60 as a starting point. then shoot to or three times as many subs at least.

 

this would give the Star Adventurer a better chance to keep on track, and you should get tighter stars, with less bloat.

 

Maybe try and get 100 or so 60 second shots at least. another option would be 200 x 30 second shots.

 

I got this using 15 second subs, but I am Bortle 1.   

 

Thanks for the suggestions, I will probably lessen my sub length to help with my not so perfect guiding.  Awesome image btw! 


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#6 Spaceman 56

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Posted 10 December 2023 - 04:00 PM

Thanks for the suggestions, I will probably lessen my sub length to help with my not so perfect guiding.  Awesome image btw! 

I am referring to unguided imaging. 

 

back then I usually shot 30 second subs at F5.6 and the DSLR, but that night my Polar alignment was so bad that 30 second subs had bad trails.

so I move down to 25 seconds, and then 20 seconds. I still had trails, so in desperation I tried 15 seconds.

 

at 15 seconds I did not have trails, so that was the longest subs I could shoot.

 

you must correlate you exposure time, against the actual results your subs give you, and choose a value slightly SHORTER than the maximum.

 

meaning that if you can shoot 25 second subs and see trails, but at 22 seconds you dont see trails (the maximum value) then opt for 20 seconds

and you should be safe. these same theories apply even when you get a much better mount and move up to long exposures.

 

I know this because I recently bought a CEM-120 mount and the first experiment I did was to see how long I could shoot unguided.

I managed 900 seconds, which told me the mount was good.  smile.gif


Edited by Spaceman 56, 10 December 2023 - 04:01 PM.

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#7 danny1976

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Posted 10 December 2023 - 07:15 PM

You didn’t mention your main imaging scope. Anyhow you should aim for at least 10h(around F5) and better 20h to get a good quality picture.


Edited by danny1976, 10 December 2023 - 07:16 PM.


#8 idclimber

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Posted 10 December 2023 - 07:33 PM

Normally I would agree with Starman on the exposures. I also agree with danny and others about more integration time. Then I looked at your image in your first post. Nice round stars and you can see some nebulosity. 

 

You do not need shorter exposures unless you are clipping the high end. As such I am inclined to advise leaving it alone. If you know how to check for clipped pixels, then how many do you have? If not post a link to a raw light sub and we can measure and better yet show you how. What software do you have to view a raw file?

 

I would otherwise direct you to capture one more night of data that you can add to the precious attempt. This is how you increase integration time. The key is to have the camera or scope the same rotation relative to the base plate and point at the same spot. What I used to do is make sure the camera and fitter wheel were perfectly parallel to the base plate on the mount. Alternatively if you prefer a plate solve it will tell you the rotation angle. You need to match within 180 degrees on a 360 circle. 

 

Pointing at the same spot is a lot harder without two axis goto. But getting to the same spot so your next set of data lines up with the previous set is worth figuring out how to do. Otherwise you are stuck with one night of data.


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#9 Plorimor

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Posted 12 December 2023 - 11:16 AM

So I was able to get about 2 hours on Pleiades last night from a bortle 4 zone! Happy with the results compared to my first try, but confused as to what could be causing the diffraction spikes/artifacts on the stars Alycone + Atlas..

48 x 150sec exposures this time

Here’s the image: https://imgur.com/a/ubrpe8E


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