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My First Nebula

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#1 flyersguy85

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Posted 11 August 2022 - 06:35 AM

Hey all,

The other night I was photographing NGC 7000 with my stock Nikon 750D with a 400mm lens. This was my first time attempting a nebula and I didn't know what to expect. As you can see in the attached image, I barely saw anything but faint stars in both the raw and stacked. I only got around 3 hours of exposure and couldn't take any dark frames, but I at least expected to see some outline or differentiation from the sky. I am in a bortles 8ish. Is this to be expected with a stock camera at such low total exposure time?

Thanks

 

Edit: The stacked image is Autosave.jpg and the sample exposure is NG 7000.

 

Autosave.jpg

 

NG 7000.jpg


Edited by flyersguy85, 11 August 2022 - 07:24 AM.


#2 matt_astro_tx

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Posted 11 August 2022 - 06:55 AM

How many individual exposures did you take?  What software did you use to process them?



#3 starrycanuck

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Posted 11 August 2022 - 07:12 AM

Hey all,

The other night I was photographing NGC 7000 with my stock Nikon 750D with a 400mm lens. This was my first time attempting a nebula and I didn't know what to expect. As you can see in the attached image, I barely saw anything but faint stars in both the raw and stacked. I only got around 3 hours of exposure and couldn't take any dark frames, but I at least expected to see some outline or differentiation from the sky. I am in a bortles 8ish. Is this to be expected with a stock camera at such low total exposure time?

Thanks

You don't mention what post-processing or stretching was done on the data. What exposure time and ISO did you use? I suspect there is nebula data there but needs to be teased out.

 

Bortle 8 and any OSC camera make nebulas a challenge.



#4 flyersguy85

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Posted 11 August 2022 - 07:23 AM

How many individual exposures did you take?  What software did you use to process them?

60 second exposures for a total of about 200 total. Unfortunately when I went longer I started to get pretty severe vignetting for some reason.

 

I used DSS for stacking and these are unprocessed. One is a sample unstacked (NG 7000) and the other is stacked (Autosave). The processed one (not shown here) was done via Photo Shop and I just corrected the color of the sky. When I did that, I still saw nothing.



#5 matt_astro_tx

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Posted 11 August 2022 - 07:24 AM

So you're saying these images are straight out of DSS.  You didn't do anything to them?



#6 flyersguy85

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Posted 11 August 2022 - 07:25 AM

You don't mention what post-processing or stretching was done on the data. What exposure time and ISO did you use? I suspect there is nebula data there but needs to be teased out.

 

Bortle 8 and any OSC camera make nebulas a challenge.

 

One is jsut a sample exposure (NG 7000.jpg) and the other is just the stacked result (Autosave.jpg) via DSS. Exposure was 60 seconds and ISO was 1600.

 

Thanks for the reply.



#7 soojooko

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Posted 11 August 2022 - 07:40 AM

Are you sure your camera was pointing at the right place? I cant see any nebulosity whatsoever in the second pic.

 

Can you give us your full gear list?



#8 flyersguy85

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Posted 11 August 2022 - 07:47 AM

Are you sure your camera was pointing at the right place? I cant see any nebulosity whatsoever in the second pic.

 

Can you give us your full gear list?

CEM 40 with ipolar, Nikon 750D with 400mm lens, ZWO ASI290MM Mini Guide camera, ZWO Mini Guide Scope. Everything seemed to be aligned and balanced.



#9 soojooko

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Posted 11 August 2022 - 08:19 AM

CEM 40 with ipolar, Nikon 750D with 400mm lens, ZWO ASI290MM Mini Guide camera, ZWO Mini Guide Scope. Everything seemed to be aligned and balanced.

Right - yes. I can see where it's at now. Looking at the stars, I think the North American nebula is in the very bottom left of your frame. But there no nebulosity at all in either of your pics. We would need the raw/tiff file to be able to tell properly as jpegs just dont cut it.


Edited by soojooko, 11 August 2022 - 08:19 AM.


#10 flyersguy85

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Posted 11 August 2022 - 08:31 AM

Right - yes. I can see where it's at now. Looking at the stars, I think the North American nebula is in the very bottom left of your frame. But there no nebulosity at all in either of your pics. We would need the raw/tiff file to be able to tell properly as jpegs just dont cut it.

So would you say that I just wasn't aligned properly and was off target? In the raws I see about the same and no sign of a nebula. Unfortunately they are too large to upload here.

 

Edit: Most of my imaging is taking place on my back deck where i barely have visual of Polaris. Ipolar confirmed it was aligned, but perhaps something happened there...I'm not sure.


Edited by flyersguy85, 11 August 2022 - 08:33 AM.


#11 soojooko

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Posted 11 August 2022 - 08:39 AM

So would you say that I just wasn't aligned properly and was off target? In the raws I see about the same and no sign of a nebula. Unfortunately they are too large to upload here.

The framing isn't perfect - but really not far off at all. As far as I can see, its roughy like this: https://imgur.com/a/ChqhG7H

 

You should be able to see the nebulosity. Have you tried aggressively stretching your raw files to see what reveals itself?


Edited by soojooko, 11 August 2022 - 08:40 AM.


#12 flyersguy85

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Posted 11 August 2022 - 08:48 AM

The framing isn't perfect - but really not far off at all. As far as I can see, its roughy like this: https://imgur.com/a/ChqhG7H

 

You should be able to see the nebulosity. Have you tried aggressively stretching your raw files to see what reveals itself?

I have not.  As someone very new to this, I was aware that was an option. How would one go about doing that?

 

Also, with a nebula, how do you get good framing? I know with galaxies I can take an exposure and easily see them (even if they are really small with my 400mm lens). But with nebula, they seem to be very faint.



#13 FrostByte

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Posted 11 August 2022 - 08:53 AM

Do you have any image processing software already? One of the first steps when processing an image is to neutralize the background and remove any light pollution gradients, which would clean up the washed-out background and would start showing some of the nebula. If you want to upload your stack somewhere (google drive, dropbox, etc) I'd be glad to show you how to do this with your image.



#14 adosaj

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Posted 11 August 2022 - 08:55 AM

You should go ahead and take some dark frames at the least and also flats if you have the image train still together. Darks will help a lot. I don’t use DSS, does it do any sky subtraction? If you are imaging a nebula in bright sky conditions sky subtraction will also help a lot. 
 

Anil



#15 soojooko

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Posted 11 August 2022 - 08:59 AM

I have not.  As someone very new to this, I was aware that was an option. How would one go about doing that?

 

Also, with a nebula, how do you get good framing? I know with galaxies I can take an exposure and easily see them (even if they are really small with my 400mm lens). But with nebula, they seem to be very faint.

Ah - ok. It depends on what computer and software you own. Do you have anything like photoshop or similar? I would suggested doing a search for a basic 'astrophotography how to stretch' tutorial.

 

Others have suggested taking darks or doing a background removal - but I would just try to get some nebulosity to reveal itself first. Even if it's a bit crude. At the end of the day - if the data isn't there, no amount of calibration or processing is going to help.



#16 cinenosin

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Posted 11 August 2022 - 09:10 AM

Sometimes a video can help understand new concepts, such as the importance of stretching.  Here is a free video that may help: https://youtu.be/DY1GEVA4Su4.



#17 flyersguy85

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Posted 11 August 2022 - 09:31 AM

Do you have any image processing software already? One of the first steps when processing an image is to neutralize the background and remove any light pollution gradients, which would clean up the washed-out background and would start showing some of the nebula. If you want to upload your stack somewhere (google drive, dropbox, etc) I'd be glad to show you how to do this with your image.

I have processed it to neutralize the background and got it to a reasonably decent sky in Photo Shop. I appreciate your offer to take a look and will upload to google drive when I get home today! Do you want all the raws or what are you looking for?

 

Thanks!



#18 flyersguy85

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Posted 11 August 2022 - 09:33 AM

You should go ahead and take some dark frames at the least and also flats if you have the image train still together. Darks will help a lot. I don’t use DSS, does it do any sky subtraction? If you are imaging a nebula in bright sky conditions sky subtraction will also help a lot. 
 

Anil

I don't have things hooked up anymore unfortunately. I am going to try again Saturday night and will be sure to take darks.



#19 flyersguy85

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Posted 11 August 2022 - 09:35 AM

Ah - ok. It depends on what computer and software you own. Do you have anything like photoshop or similar? I would suggested doing a search for a basic 'astrophotography how to stretch' tutorial.

 

Others have suggested taking darks or doing a background removal - but I would just try to get some nebulosity to reveal itself first. Even if it's a bit crude. At the end of the day - if the data isn't there, no amount of calibration or processing is going to help.

Understood. As far as framing goes, is it best to just take an exposure and check the frame? I have done that with galaxies but i wasn't sure if nebulae would show enough to use the same strategy (since I didn't see anything on test shots).



#20 soojooko

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Posted 11 August 2022 - 09:40 AM

Understood. As far as framing goes, is it best to just take an exposure and check the frame? I have done that with galaxies but i wasn't sure if nebulae would show enough to use the same strategy (since I didn't see anything on test shots).

Yep - thats what I do. As you are using a DSLR, take 30-60 second exposures with a high ISO. Just enough so you can see some nebulosity appearing. Adjust the frame and shoot again. etc. I used a Canon 700D before, and found that 60 seconds at 1600ISO was usually enough to reveal something if its there.

 

Having said that, you are in a bortle 8 zone. Im B4 here, so I'm not sure my advice is valid! 



#21 FrostByte

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Posted 11 August 2022 - 09:46 AM

I have processed it to neutralize the background and got it to a reasonably decent sky in Photo Shop. I appreciate your offer to take a look and will upload to google drive when I get home today! Do you want all the raws or what are you looking for?

 

Thanks!

Just the unstretched stack, straight out of DSS.



#22 flyersguy85

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Posted 11 August 2022 - 10:00 AM

Just the unstretched stack, straight out of DSS.

The Autosave.jpg in the original post is straight out of DSS including bias frames except for darks. A jpg obviously isn't going to show enough, so i can upload the uncompressed file to google drive.



#23 Ar3s701

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Posted 11 August 2022 - 10:25 AM

This might be a dumb question, but did DSS stack all your images? I've had issues in the past where it goes through the whole process and then only stacks 1 light frame.



#24 fmendes

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Posted 11 August 2022 - 11:17 AM

I didn't see any mention to filters. Bortle 8 without any filter won't show much, as light pollution will overpower the light of the nebula.



#25 RPitts62

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Posted 11 August 2022 - 11:52 AM

I'm a relative newbie as well, so I probably can't answer some of your questions, but my most recent target was NGC7000 and my total exposure time was very similar to yours. I was using a guided star tracker and a wide field refractor (250mm), un-modded DSLR and I managed to get a decent image (for me anyway) with 3 hours and twenty minutes of data. I shot 100 subs at 2 minutes each so our data accumulation is almost identical. The biggest difference I see is your amount of light pollution you are having to deal with. I shot from a pretty dark sky (Bortle 2). Bortle 8 sounds pretty severe and will certainly affect your ability to frame and shoot your target.

 

I think ISO 1600 may be a bit high. Sure it's letting in more light, but with all the light pollution it sounds like you might be getting a lot of unwanted ambient light as well. Cameras are all different, so that will probably take some experimentation on your part to see what suits your camera. For mine, which is a Canon, the sweet spot seems to be about ISO 800. 

 

Here is one of my single subs from a few weeks ago. 2 minutes each at ISO 800. Again, this is from Bortle 2 skies, but I could just make out the nebulosity in my test exposures that allowed me to frame it pretty well. If you have the ability to travel to darker skies that will certainly help.

 

Also, calibration frames are important! don't skip those.

 

Randy

Attached Thumbnails

  • Single Sub.jpg

Edited by RPitts62, 11 August 2022 - 11:53 AM.



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