Contains:Crescent nebula, NGC 6888
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The Crescent Nebula, 




    

        Don Curry
The Crescent Nebula

The Crescent Nebula

Technical card

Resolution: 1568x1148

Dates: June 11, 2018

Frames:
Astrodon 5nm Halpha: 104x1800" -23C bin 2x2
Astrodon 5nm OIII: 60x1800" bin 2x2

Integration: 82.0 hours

Darks: ~18

Flats: ~12

Bias: ~50

Avg. Moon age: 26.90 days

Avg. Moon phase: 7.64%

Bortle Dark-Sky Scale: 3.00

Mean SQM: 20.00

Mean FWHM: 3.40

Astrometry.net job: 2155922

RA center: 303.034 degrees

DEC center: 38.358 degrees

Pixel scale: 0.810 arcsec/pixel

Orientation: 78.998 degrees

Field radius: 0.219 degrees

Locations: Home Observatory, Kingman, Arizona, United States

Data source: Backyard

Description

A real labor of love and a challenge imaging this from my backyard. I'm dealing with extreme hot nightly temperatures all night at 80 to 85F. Cooler is running at 100% for most the night. I may need to stop imaging this for 1 week until the nightly temperature drops to 68F ; but then I'll be approaching the start of the monsoon season.
This is about 10 hours of data so far and teasing out the OIII has been a real challenge along with the hot nightly temperatures with rolling clouds spoiling my OIII data collection from last night. I had to drop 1 hours of data due to this from my OIII.
The current final image has about 5 additional hours of OIII ; but curious to me I thought I would see much more detail and if I stretch the data more then my stars start to blow up unless maybe I try a star mask.
Unable to maintain -25C for my cooler during the hot summer all night weather conditions in Northern Arizona. I'm running at -18C and my darks were taken at a -25C so I may be having problems with my darks taken during the winter at -25C without knowing my first summer in this weather the challenges I'm having.
I still have used my flat, dark, bias library anyway during this updated final image and it did seem to help the overall quality of the master final image.
Finally was able to bring out more from the OIII data set. I went back and very carefully hand picked the very best images to stack and it made a big difference in the final stack. The OIII data now is nearly twice that of the Ha all 30 minute guided from my backyard. I used about 16 OIII's and about 8 Ha's all 30 minute guided.
Now for another update : I'm up to already about 24 30 minute OIII guided subs and 12 Ha 30 minute guided subs. The overall background noise has significantly decreased in NGC 6888.
At my location humidity is extremely low with clear sky's forecasted all week long ; thus I'm taking advantage of this imaging at 4.5 hours per night with switching back from OIII to Ha night after night. I'm sure by end of the week I may be closer to 40 hours of collected data and will be very interesting to see the results by then.
I applied a mask clone copy in PI to bring out more detail in the Crescent Nebula structure without affecting the centroid of the stars as much. I could have applied DBE to this updated image but thought the idea would not look good due to the fact from prior experiences imaging from this part of the sky the overall background is rich in Ha thus I left the background alone and let it stand on its own as is.
Well after tonight's session I should be approaching close to 30 hours of data and weather here calls for clear hot low humidity sky's for the next 2 weeks. I am not doing most of this at all yet with automation ; as I'm setting alarm once every hour from midnight until 2:30 A.M. to do refocus with @focus3.
Hopefully my final edit for this season. I was careful not to push the data to much as I wanted to apply additional curves but stars were beginning to oversaturate. I may need to go into PI and do a PSF on the stars. I did attempt a deconvolution in CCD Stack but did not like the results it made on my larger stars although it did sharpen the average smaller stars much better.
Revisions R & S were both stacked and properly calibrated in Maxim DL5 then in linear brought into Pixinsight 1.8 tp do PSF function with 50 sample star points and a deringing mask,. Global dark was set at a .34 mark. I was still getting artifacts at 0.08 through .17 and .22 but left it at .34 for compromise and it seemed to work very well. Revision S was balanced for even contrast between Ha and OIII balance using Photoshop CC. The OIII was ending up being way more prominent in the final stacked master and was somewhat difficult to get it under control. Next summer I'll probably will need to lower sub exposures down to 900 or 1200 second subs. to avoid oversaturation of stars. My seeing is not allowing for the longer exposure runs from what I could observe. I still enjoyed the challenge from my backyard to try and push for as much detail as what I obtained and hope for interesting results in the future.

Comments

Author

trombone76
Don Curry
License: Attribution-NonCommercial-NoDerivs Creative Commons
1500
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Revisions

  • The Crescent Nebula, 




    

        Don Curry
    Original
  • The Crescent Nebula, 




    

        Don Curry
    G
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        Don Curry
    I
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        Don Curry
    L
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    O
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    Q
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    R
  • Final
    The Crescent Nebula, 




    

        Don Curry
    S

R

Finally processed in Pixinsight using PSF function and the results were much tighter stars and inner detail.

Sky plot

Sky plot

Histogram

The Crescent Nebula, 




    

        Don Curry