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How much exposure time needed to image Barnard's Loop in Orion constellation?

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#1 Greenleafs91

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Posted 08 April 2020 - 10:30 PM

Pretty new to astrophotography. For background info, I live in area with Bortle 8 skies (yay...). Modified Canon 600D with LPF-2 removed only. Trying to take 2 sec exposures of Orion constellation untracked and will use DSS for stacking + Ps for post processing. Wondering if it is possible to get all the colors and such to image Barnards Loop as I think it is so cool and if so, how much exposure time (estimated of course) would I potentially need? For post processing, I just stretch the image multiple times as a whole (haven't tried stretching each color individually) and then use the subtract technique to darken skies (and get rid of some of that permeating red glow) then throw in some curves and saturation. Still learning so I don't know if it is a matter of enough exposure or maybe I'm doing things wrong in post processing. Any advice much appreciated! To clear skies. 



#2 lemonade

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Posted 08 April 2020 - 11:53 PM

Pretty new to astrophotography. For background info, I live in area with Bortle 8 skies (yay...). Modified Canon 600D with LPF-2 removed only. Trying to take 2 sec exposures of Orion constellation untracked and will use DSS for stacking + Ps for post processing. Wondering if it is possible to get all the colors and such to image Barnards Loop as I think it is so cool and if so, how much exposure time (estimated of course) would I potentially need? For post processing, I just stretch the image multiple times as a whole (haven't tried stretching each color individually) and then use the subtract technique to darken skies (and get rid of some of that permeating red glow) then throw in some curves and saturation. Still learning so I don't know if it is a matter of enough exposure or maybe I'm doing things wrong in post processing. Any advice much appreciated! To clear skies. 

To be completely honest, I don't think you will be able to collect enough 2sec untracked exposures to EVER see much of barnard's loop from bortle 8. I doubt that it's even possible from pristine desert skies. The orion nebula will come out in the images but it will be very noisy and not anything like the wide cloudy vistas you've seen on astrobin. The orion nebula itself is the brightest nebula in the sky and it's hard even to do that alone with 2 sec exposures. Add to that the fact that you live under high light pollution, and you're looking at quite a daunting task. It takes tens of hours from the city to get enough data on the other brighter parts of the area like the horsehead nebula or M78. The faint black dust would take probably a whole season's worth of clear nights even with the proper equipment. Even if it is possible, I don't think you'll be able to do it before Orion is under the horizon for the year. Unfortunately this is probably the worst time of year to start with DSO astrophotography especially with your setup. Everything coming up this time of year is faint and tiny and hard to find. You might find it less frustrating and have a better experience if you have the patience to wait for the summer targets and maybe save up money for a star tracker.

Also, for processing, with a one shot color camera like yours you probably don't need to stretch the individual color channels. Sometimes applying certain processes to certain channels can make subtle improvements to the image but they are very low on the priority list for a beginner IMO.

I started out similarly, and the orion nebula was about the only thing I could even get anything out of. Good luck!


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#3 AstroBrett

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Posted 09 April 2020 - 12:35 AM

That will depend on the f-ratio of the optical system you are planning to use. I had no trouble imaging Barnard's loop from my mag 21.5 (Bortle 2-3) skies using 45 subframes of 90s with an f/4.5 lens.  I think 25-30 subframes of 90s would have been sufficient to detect it.  Of course, a faster f-ratio lens would cut down on the exposure time needed. 

 

I'm rather doubtful about your plan to use 2-sec subframes. The signal will be barely above the noise floor, and it's going to be difficult to acquire a sufficient number of subframes to gain any appreciable signal-to-noise ratio (SNR). And this time of year with Orion well past the meridian at astronomical twilight, it's low position in the sky is going to make things nearly impossible, particularly under Bortle 8 conditions.

 

I'd give it a try as you will gain valuable experience as you go, and I wish you best of luck.

 

Brett


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#4 17.5Dob

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Posted 09 April 2020 - 09:55 PM

Pretty new to astrophotography. For background info, I live in area with Bortle 8 skies (yay...). Modified Canon 600D with LPF-2 removed only. Trying to take 2 sec exposures of Orion constellation untracked and will use DSS for stacking + Ps for post processing. Wondering if it is possible to get all the colors and such to image Barnards Loop as I think it is so cool and if so, how much exposure time (estimated of course) would I potentially need? For post processing, I just stretch the image multiple times as a whole (haven't tried stretching each color individually) and then use the subtract technique to darken skies (and get rid of some of that permeating red glow) then throw in some curves and saturation. Still learning so I don't know if it is a matter of enough exposure or maybe I'm doing things wrong in post processing. Any advice much appreciated! To clear skies. 

I was able to capture it from my Bortle 7+/ 8-  backyard by shooting 250 X 45" subs at f5 ....2 1/2 hrs total

Two sec exposures are going to extremely rough to get anything above the read noise floor, even after stacking, because read noise is cumulative. You would need to shoot 5,625 subs, so you would end up with 23X more noise than my shots, if you used a good low read noise camera. The 600D is twice as noisy as my camera, so the end noise would be 46X worse, than mine.

I can't even conceive of trying to stack 5,625 subs, let alone, how many SD cards it's going to take to shoot that many subs.

 


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#5 Greenleafs91

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Posted 14 April 2020 - 12:32 AM

Thanks for all the wonderful knowledge and advice! Definitely thinking that I have to travel a bit to a darker sky. And yeah, I don't know what I would be able to shoot in terms of DSO these coming months. I guess I'll have to search the web. 

 

To be completely honest, I don't think you will be able to collect enough 2sec untracked exposures to EVER see much of barnard's loop from bortle 8. I doubt that it's even possible from pristine desert skies. The orion nebula will come out in the images but it will be very noisy and not anything like the wide cloudy vistas you've seen on astrobin. The orion nebula itself is the brightest nebula in the sky and it's hard even to do that alone with 2 sec exposures. Add to that the fact that you live under high light pollution, and you're looking at quite a daunting task. It takes tens of hours from the city to get enough data on the other brighter parts of the area like the horsehead nebula or M78. The faint black dust would take probably a whole season's worth of clear nights even with the proper equipment. Even if it is possible, I don't think you'll be able to do it before Orion is under the horizon for the year. Unfortunately this is probably the worst time of year to start with DSO astrophotography especially with your setup. Everything coming up this time of year is faint and tiny and hard to find. You might find it less frustrating and have a better experience if you have the patience to wait for the summer targets and maybe save up money for a star tracker.

Also, for processing, with a one shot color camera like yours you probably don't need to stretch the individual color channels. Sometimes applying certain processes to certain channels can make subtle improvements to the image but they are very low on the priority list for a beginner IMO.

I started out similarly, and the orion nebula was about the only thing I could even get anything out of. Good luck!

 

 

That will depend on the f-ratio of the optical system you are planning to use. I had no trouble imaging Barnard's loop from my mag 21.5 (Bortle 2-3) skies using 45 subframes of 90s with an f/4.5 lens.  I think 25-30 subframes of 90s would have been sufficient to detect it.  Of course, a faster f-ratio lens would cut down on the exposure time needed. 

 

I'm rather doubtful about your plan to use 2-sec subframes. The signal will be barely above the noise floor, and it's going to be difficult to acquire a sufficient number of subframes to gain any appreciable signal-to-noise ratio (SNR). And this time of year with Orion well past the meridian at astronomical twilight, it's low position in the sky is going to make things nearly impossible, particularly under Bortle 8 conditions.

 

I'd give it a try as you will gain valuable experience as you go, and I wish you best of luck.

 

Brett

 

 

I was able to capture it from my Bortle 7+/ 8-  backyard by shooting 250 X 45" subs at f5 ....2 1/2 hrs total

Two sec exposures are going to extremely rough to get anything above the read noise floor, even after stacking, because read noise is cumulative. You would need to shoot 5,625 subs, so you would end up with 23X more noise than my shots, if you used a good low read noise camera. The 600D is twice as noisy as my camera, so the end noise would be 46X worse, than mine.

I can't even conceive of trying to stack 5,625 subs, let alone, how many SD cards it's going to take to shoot that many subs.

 



#6 2ghouls

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Posted 14 April 2020 - 09:23 AM

I agree with others that with 2" exposures from Bortle 8, I wouldn't expect to be able to bring out the loop very well, if at all. 

 

I disagree with others that it's not possible from dark skies, even untracked, even with 2" exposures. You didn't mention what lens (focal length and focal ratio) which will make a big difference too. Faster/wider/bigger lenses will be better in this context.

 

I took this shot without a tripod, just the camera and lens, on the ground angled using a rock. Orion was very low in the sky. This is just 60 x 6 seconds (5 min integration) from Bortle 3. If I would have done 20x that, it would be much cleaner. Camera: Nikon d800 mod, Lens: Sigma 105mm Art at 1.8

 

orion-notripodd.jpg

 

In a recent video I did (see signature), I saw a bit of the loop in my stack from Bortle 6 with 2 sec. exposures using an UNMODIFIED 5D mk 3. 

 

My advice is always to just try, you might be surprised!

 

Clear skies, Nico

 




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