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Imaging the Helix Nebula without a telescope or a star tracker

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#1 hdoraisamy

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Posted 18 September 2020 - 06:56 AM

I am really interesting in imaging the Helix nebula from a Bortle 5 location in Southeast Pennsylvania with my Canon EOS Rebel T6 DSLR and a Pentax 130mm lens without a telescope. According to Stellarium, the target should be visible in the Southeast sky after sunset.

 

However, I am not able to use my star tracker at this time since I am waiting on my reticle illuminator for polar alignment to arrive from China.

 

I was thinking of taking about 300 2-second subs with some darks, bias and flats and stacking them in DSS. Would this give me a decent image of my target (this worked for M31)? I don't have a filter, nor is the camera modified.

 

I know this is a dim target, so i do expect some heavy post processing. 

 

Thanks!

 



#2 D_talley

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Posted 18 September 2020 - 08:02 AM

This is not an object I would try to image. It is very small compared to M31 that you were successful with.  Also it is very dim and most of its light is in the Ha range, which your unmodified camera will not see.  You suggested taking only 10 minutes worth of 2 second lights, which is not enough. I normally shoot for 10 to 15 hours when I shoot the Helix and that is not enough in my astro camera. 

 

I would try something brighter and bigger.


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#3 B 26354

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Posted 18 September 2020 - 09:35 AM

The https://astronomy.to.../field_of_view/ website is great for calculating a visual- or imaging-setup's FOV. The Helix nebula (NGC7293) is approximately 18 arc-minutes in diameter -- a bit more than half the size of the Moon -- so with a 130mm lens on your APS-C Canon, it'll only be about this big, in the frame:

 

Helix - APS-C - 130mm lens.jpg

 

So your test-run of photos will give you some of the information you'll need for determining how much total exposure will be required... but with that lens, the nebula itself is gonna be pretty small.

 

And as "D talley" points out, ten minutes of exposure on this very dim, primarily "red" target, isn't anywhere close to being enough... even with great equipment, under ideal conditions.

 

But what the heck. Give it a try... and maybe increase your trial run to 3,000 x 2-seconds.  biggrin.png

 

Most of us started the AP learning-process at the "beginning", and have slowly made progress through a never-ending series of successes and failures. Practice, practice, and more practice is the only way you'll discover what your equipment and observing conditions really will allow you to accomplish.

 

And most important of all... have fun! And definitely post your results!    waytogo.gif


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#4 hdoraisamy

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Posted 18 September 2020 - 03:55 PM

The https://astronomy.to.../field_of_view/ website is great for calculating a visual- or imaging-setup's FOV. The Helix nebula (NGC7293) is approximately 18 arc-minutes in diameter -- a bit more than half the size of the Moon -- so with a 130mm lens on your APS-C Canon, it'll only be about this big, in the frame:

 

attachicon.gifHelix - APS-C - 130mm lens.jpg

 

So your test-run of photos will give you some of the information you'll need for determining how much total exposure will be required... but with that lens, the nebula itself is gonna be pretty small.

 

And as "D talley" points out, ten minutes of exposure on this very dim, primarily "red" target, isn't anywhere close to being enough... even with great equipment, under ideal conditions.

 

But what the heck. Give it a try... and maybe increase your trial run to 3,000 x 2-seconds.  biggrin.png

 

Most of us started the AP learning-process at the "beginning", and have slowly made progress through a never-ending series of successes and failures. Practice, practice, and more practice is the only way you'll discover what your equipment and observing conditions really will allow you to accomplish.

 

And most important of all... have fun! And definitely post your results!    waytogo.gif

Thank you both! I am glad i checked, otherwise I would have wasted the entire evening on this moonless night

 

Would M15 or M13 be a better target for my situation?

 

Thanks!



#5 B 26354

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Posted 18 September 2020 - 05:11 PM

M13's gettin' a little low in the west. M15's much better placed... but it's only 12'x12', so it's gonna be even smaller than the Helix. frown.gif


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#6 AtmosFearIC

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Posted 19 September 2020 - 01:58 AM

It might be smaller but it is significantly brighter which matters with 2s exposures :)


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#7 hdoraisamy

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Posted 19 September 2020 - 05:30 AM

It might be smaller but it is significantly brighter which matters with 2s exposures smile.gif

Thank you :)




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