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Alnitak Nebula Complex in Orion – 600Da & OPT Triad Ultra

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#1 jgraham

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Posted 10 October 2019 - 07:58 PM

Telescope: ES DHL Comet Hunter MN6 at f/4.8, Orion Atlas EQ-G
Camera: Full-spectrum Modified Canon 600D (Rebel T3i)
Filter: 2” OPT Triad Ultra Hb, OIII, Ha, SII filter
Guide scope: Williams Optics 50mm, Meade DSI Pro III, PHD
Exposure: 40x120sec, ISO 1600 saved as RAW
Darks: Internal (Long Exposure Noise Reduction On)
Flats: 32x1/50sec, Tee-shirt flats taken at dusk
Average Light Pollution: Red zone, Bortle 8, fair transparency
Lensed Sky Quality Meter: 18.5 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

 

Alnitak (10-8-2019)-1j.jpg

 

This image was the last in a brief series to test the OPT Triad Ultra with my full-spectrum modified Canon 600D. I left the field in its native aspect ratio to squeeze everything that I could from this system, cropping just a bit to clean up around the edges. Overall I’m very happy with the results.

 

This is a very busy region of the sky near Alnitak, the eastern star in the belt of Orion. Alnitak is the brilliant star at the top of this field. NGC  2024 (the Flame Nebula) is to the left and the beautiful red emission nebula IC 434 drapes down the center of the field with the iconic Horsehead Nebula (Barnard 33) silhouetted it. To the left are the reflection nebula NGC 2023 and the tiny IC 435. To the lower right is Sigma Orionis, a wonderful complex of stars that is a fine target for binoculars and small telescopes. In larger scopes it resolves into a wonderful group of double and triple stars.


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#2 StarBurger

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Posted 10 October 2019 - 08:18 PM

Like it very much, but just a question-is there a reason you used LENR for the image?

Obviously it worked OK as it should, but doubling the capture time ?



#3 jgraham

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Posted 10 October 2019 - 08:53 PM

I always use LENR. It takes exactly zero additional time to take my subs. I use the same procedure that I have always used; start imaging as soon as the field clears the trees and stop when it reaches the meridian. My subs are clean and clear without any hot or cold pixels and perfectly matched lights and darks. 40 subs is plenty to work with. As I have described many times before conventional image calibration is based on a difference of means. LENR uses a different statistical model called paired differences. When there is a blocking factor it is appropriate to use paired differences. When there is no blocking factor paired differences gives the same result as a difference in means. With uncooled cameras temperature is usually a strong blocking factor and therefore it is appropriate to use paired differences; lights paired with darks taken at nearly the same temperature. After many years of conventional image calibration I spent about a year studying LENR and how it works. (Statistical data analysis is a big part of my job.) Once I was satisfied that I liked it, I have been using it every since. I still take darks, I just never see them. I let the camera do it's work while I get some sleep. :)

 

I like it, I use it, most people hate it, and ignore it, and I'm okay with that. It's my Secret Sauce. :)



#4 bobharmony

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Posted 10 October 2019 - 09:14 PM

That is a fine image.  The filter (or your processing, or both) does a fine job of keeping Alnitak under control.  My rendition of this area has diffraction spikes all the way across the field of view, and a rather bloated star core as well.  Well done!

 

Bob



#5 ChristopherBeere

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Posted 11 October 2019 - 04:28 PM

I always use LENR. It takes exactly zero additional time to take my subs. I use the same procedure that I have always used; start imaging as soon as the field clears the trees and stop when it reaches the meridian. My subs are clean and clear without any hot or cold pixels and perfectly matched lights and darks. 40 subs is plenty to work with. As I have described many times before conventional image calibration is based on a difference of means. LENR uses a different statistical model called paired differences. When there is a blocking factor it is appropriate to use paired differences. When there is no blocking factor paired differences gives the same result as a difference in means. With uncooled cameras temperature is usually a strong blocking factor and therefore it is appropriate to use paired differences; lights paired with darks taken at nearly the same temperature. After many years of conventional image calibration I spent about a year studying LENR and how it works. (Statistical data analysis is a big part of my job.) Once I was satisfied that I liked it, I have been using it every since. I still take darks, I just never see them. I let the camera do it's work while I get some sleep. smile.gif

 

I like it, I use it, most people hate it, and ignore it, and I'm okay with that. It's my Secret Sauce. smile.gif

I used to shoot darks as a matter of calibration discipline but lately I don't bother.

 

I was considering using LENR on my 6DMK2 -  I will give it a go and see if it's any good.


Edited by ChristopherBeere, 12 October 2019 - 01:51 AM.


#6 jgraham

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Posted 12 October 2019 - 05:50 AM

When I first started using it the hardest part was waiting for the camera to take each dark. It took a lot of getting used to. That's why I spent the better part of a year evaluating it. While it may seem like it is a frustrating waste of time, the camera is actually doing a lot of work without you having to do anything other than being a little patient. Now I don't even think about it. It just does its thing. What really convinced me was the first year that I imaged right through the heat of summer with sensor temperatures over 40C without any problems. Even now having access to modern cooled cameras like the ASI294MC Pro and ASI071MC Pro I still enjoy using my trusty modified DSLRs. They are just so simple and work so well.

Enjoy!

#7 Brett Waller

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Posted 12 October 2019 - 09:41 AM

A very nice image.

 

Long Exposure Noise Reduction On (LENR) works fine and matches the dark frames as precisely as the electronics are capable of doing.  But let's be clear, your statement that "It takes exactly zero additional time to take my subs" is incorrect at best, and somewhat misleading. LENR takes a light frame and then follows it with a dark frame of the same exposure, so you collect half the light frame subs you would get with traditional processing. This is the main reason most people do not use LENR since you lose half of your potential imaging time.  For most locations where clear nights are not common, this is a big disadvantage.



#8 jgraham

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Posted 12 October 2019 - 01:19 PM

Round and round we go, just like old times...

 

Here in SW Ohio we get an average of 50 clear nights per year, or about 1 per week, using them all is my goal. I image from dusk to dawn to squeeze every useful minute out of every evening.

 

With LENR you don't need as many source frames because the source images are clean and clear. Doubling the number of subs from 40 to 80 will only improve the SNR by about 40% (the square root of 2 is 1.414...), assuming that there is no improvement in the image quality.

 

There are many paths to obtaining images that the imager is happy with, this is mine. There is no One True Way.

 

I dunno, I thought that is image was gorgeous. IC 434 forms this beautiful veil of red flame draping off to the west. Not too shabby for an uncooled camera under Bortle 8 skies.

 

I went easy on the processing to keep from saturating the Flame. I kinda like erring on the side of caution anyway, I find the beauty in these object is in their subtlety.

 

Enjoy.

 

:)


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