NGC7023 - Iris Nebula  

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(@annehouw)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 5
September 23, 2018 22:46  

NGC7023

Imaging Location: My backyard (orange zone)

Telescope: Ritchey-Cassegrain  (prime focus). F=1000mm F/D=3.0

Camera: Starlight Xpress SXVR-26C OSC

Integration time: 15 hrs over 8 nights (90x600s). Heavily dithered.

Pre-processing: APP 

Average stack, quality weight, discard worst 5%, LN sigma clip kappa 3 - 1 iterations

Post Processing APP + Photoshop

APP: Calibrate background, remove light pollution, calibrate star colors on area's without nebulosity, HSL to eliminate green pixels and reduce color noise of background, DDP (20%BG, 3 sigma, 2,.5% Base), Highlight protection. 

Photoshop: Various targeted contrast stretches, noise reduction, selective sharpening, star shrinking etc.

About the object:

Diffuse reflection nebula in a molecular cloud complex. In its center a young pre-main sequence star whose stellar wind and UV radiation have carved out the cave like structure and lights up the walls. 

 

This topic was modified 4 months ago 2 times by Annehouw

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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 1844
September 25, 2018 16:41  

Wow Anne @annehouw,

That is a superb Iris Nebula 😉

Can you share more about the optics? A F/D 3.0 R.C. telescope ?

Thanks for sharing the processing details.

Cheers,

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@annehouw)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 5
September 25, 2018 17:38  

Hi Mabula,

Thanks for the wow 😀 

The telescope is a so-called "Hypergraph", made by Philipp Keller in Germany.  It is a corrected RC, meaning that it has correctors in the prime and cassegrain focus to provide for a flat surface over medium format. Using the secondary mirror it is a F/9 system, but replacing the secondary mirror with a lens corrector gives F/3 (camera in the front like with e.g. a Schmidt telescope). Actually it is a F/2.9 system, but I put a 3D printed diafragma in front of the primary mirror as I get cleaner stars that way (turned edge effect).  A mirror scope this fast is very finicky to tune. Tolerances are small. I am still in the process of re-tuning it. I had to crop the image because there is still astigmatism due to the fact that I changed the distance between the primary and secondary. Tolerance is 0,5mm.... I can spend a lot of time doing this without ever taking a pretty picture, but with no moon I also want get something nice to look at and that is  how the image of the Iris Nebula came to be. The stars could be better because the resulting image is a combination of various collimation and primary-secondary distance images. 

15 hours at F/3 is a brute force attack to overcome light pollution. The milky way is only visible with averted vision over here. So, two months to make one image  🤣 

 

Regards,

Anne

 

This post was modified 4 months ago by Annehouw

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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 1844
October 14, 2018 20:15  
Posted by: Annehouw

Hi Mabula,

Thanks for the wow 😀 

The telescope is a so-called "Hypergraph", made by Philipp Keller in Germany.  It is a corrected RC, meaning that it has correctors in the prime and cassegrain focus to provide for a flat surface over medium format. Using the secondary mirror it is a F/9 system, but replacing the secondary mirror with a lens corrector gives F/3 (camera in the front like with e.g. a Schmidt telescope). Actually it is a F/2.9 system, but I put a 3D printed diafragma in front of the primary mirror as I get cleaner stars that way (turned edge effect).  A mirror scope this fast is very finicky to tune. Tolerances are small. I am still in the process of re-tuning it. I had to crop the image because there is still astigmatism due to the fact that I changed the distance between the primary and secondary. Tolerance is 0,5mm.... I can spend a lot of time doing this without ever taking a pretty picture, but with no moon I also want get something nice to look at and that is  how the image of the Iris Nebula came to be. The stars could be better because the resulting image is a combination of various collimation and primary-secondary distance images. 

15 hours at F/3 is a brute force attack to overcome light pollution. The milky way is only visible with averted vision over here. So, two months to make one image  🤣 

 

Regards,

Anne

 

Hi Anne @annehouw,

Thank you for sharing the details about the optics, that's impressive 😉

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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