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ramdom

~76 hours nebula and open cluster B59/Ced214/LBN589/NGC7762/NGC7822//Sh2-171 (c-sho)

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Total integration: ~76 hours/4556 minutes = (153x7m + 52x6m for S2) + (155x7m + 72x6m for Ha) + (168x7m + 80x6m for O3)

220721473_ngc7822_153x42052x360155x42052x360168x42080x360_4556m_76h.inline.jpg.2083e8cd38425afa05bc72d80467196e.jpg

Camera: QHY163M (16mp mono) CMOS cooled to -15 degrees C.

Telescope: Stellarvue SV70T triplet apochromat refractor @ f/4.8.

Reducer: SFFR70-APO

Mount: Paramount MyT.

Filters: Astrodon 5nm Ha, 3nm O3, 3nm S2.

Software: Sharpcap, PixInsight. 

Inline image with reduced quality uploaded to forum. Full sized higher resolution image is here: http://ram.org/images/space/scope/1.4.4.5/ngc7822_153x420+52x360+155x420+52x360+168x420+80x360_4556m_76h.jpg

NGC7822 is the designation given to young star forming complex (Berkeley 59) in the constellation Cepheus, whose surrounding environment has a distinctive skull-like appearance. The emission nebula (core region) is Sharpless 171 aka Cederalbad 214 and the wider field object with the loop/ear-like structure consists of both NGC7822 and the cluster of stars to the upper right that look like little white flecks of paint is NGC7762 (the ear within the ear). There is more to this nebula that goes down below and fleshes out the skeleton shape, but obviously doesn't fit within my FOV.

The emission nebula contains examples of objects known a "pillars of creation", active star forming regions that use the material in the nebula to shape the overall structures until there is no more raw material left creating a cavity in the middle (which is why some of these nebulae may start to look the same).  The region is 3000 light years away, so it probably is still active.  The field of view spans over 40 light years. The region also contains a supernova remnant somewhere (G118.3+0.48).

As of now, this is the target I've spent the most time on, taking 17 nights to do it all over a month (largely automated of course, but still) to end up with ~76 hours of useful data. It was a tough target for a variety of reasons but because the surrounding loop region is fainter than the central core, extra time was necessary to obtain some contrast and detail. Unlike with relatively brighter nebulae, where a few hours with each is enough and diminishing return sets in fast, I found that the longer the total exposure, the greater the contrast and detail I was able to obtain. I am confident that what you see (particularly in the nominally processed versions D and E) is what you get if you go deeper with this target---there are a lot of dark regions that are real.

Ha only image: https://www.astrobin.com/0n8mh1/C/

Aggressive processing, palette choice 1: https://www.astrobin.com/0n8mh1/0/

Aggressive processing, palette choice 2: https://www.astrobin.com/0n8mh1/B/

Nominal processing, palette choice 1: https://www.astrobin.com/0n8mh1/D/

Nominal processing, palette choice 2: https://www.astrobin.com/0n8mh1/E/

An additional frustrating thorn in my side was clouds. Multiple forecasts would state "clear", I would set up, go inside and then the clouds would come and go. There were few days of data collection where this issue didn't exist but fortunately PixInsight's image integration worked its magic and was able to register all but a few frames (though a few hours worth were weighted very low and this is after manually discarding over 50 frames that were completely cloudy). I did some integrations ignoring the worst frames but the difference was so tiny (and it was arguable as to which version was better) that I decided to use all the data I collected as long as the software didn't mind. Finally, another milestone with these images is that this is the first time I didn't rely on Photoshop to do the Hubble palette tweaking, relying only on PixInsight to do it.

My eventual goal is to do what I did with IC1396/Elephant's Trunk, which is to image in detail the Sh2-171 area in the middle to complement this widefield of the entire region. In that case, I did things the other way (core first, widefield later), but here I may be able to use this data to augment any detailed imaging of the core region.

As always, thanks for looking!

--Ram

 

Edited by ramdom
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An unusual colour palette, but I like it.  

Considering the huge length of time you have spent on this, it is very noisy if you look close in, and I wonder why, but without zooming in it looks a great image.  I don't really understand CMOS cameras as mine are CCD, so perhaps the hours are not a good comparison.

Carole 

 

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Thanks Carole, there are other colour palette choices on my astrobin page for this target.  My wife and my 11 year old daughter are my image choice consultants and they said that while the typical palette I prefer actually looks better, there's also a "sameness" to all the images (not to us APers but to laypeople) so I decided to change it up a bit!

And you're right about the noise too. I did try to reduce the noise using ACDNR which works but it changes the colour and as you note, it's only apparent when zoom in. I do it typically on most of my images but I didn't for this one - I think I'm just tired of looking at it! There apparently is another way to do denoising with Pixinsight I've not fully learnt yet (TGVdenoise) but it's on my list of things to do.  

Finally there's the issue of the pixel scale - with the 70mm scope and the sensor size, there is a slight amount of undersampling.  It's good enough for wide field but for detailed imaging a higher resolution combination would be needed.  My goal was to produce a nice wide field  image... 

--Ram

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Try this in Pixinsight. It's a nice subtle noise reduction I often use on my ASI1600MM images at non linear stage. Your camera has the same sensor so should offer a similar NR to your pixels. When you open MLT just click Noise reduction and adjust the settings in that tab.

MLT.PNG

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Wow, thank you so much - that is a much better tip than using ACDNR.  It doesn't change the image from a global perspective but does get rid of the colour noise when zoomed in. You can take a look at the result here:  http://ram.org/images/space/scope/1.4.4.5/ngc7822_153x420+52x360+155x420+52x360+168x420+80x360_4556m_76h.jpg

You know, every time I'm near completion of an image, I say to myself "patience" and not to rush things but then either due to excitement or being tired, I just rush to push it out. Thanks for your tip - I've saved the process now and should be able to apply it to other images easily. 

--Ram

 

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