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PuWe1 (Purgathofer-Weinberger 1)

Technical card

Resolution: 3868x2648

Dates: Oct. 11, 2017Oct. 17, 2017Oct. 18, 2017Oct. 19, 2017Oct. 20, 2017Oct. 21, 2017Oct. 22, 2017Oct. 25, 2017Oct. 27, 2017Oct. 28, 2017Oct. 31, 2017Nov. 1, 2017Feb. 3, 2018

ZWO H-alpha 7nm: 151x300" (gain: 225.00) bin 2x2
ZWO H-alpha 7nm: 116x400" (gain: 225.00) bin 2x2
ZWO H-alpha 7nm: 34x600" (gain: 225.00) bin 2x2
ZWO OIII: 152x400" (gain: 225.00) bin 2x2
ZWO OIII: 76x600" (gain: 225.00) bin 2x2
Orion SkyGlow 2" Astrophotography Filter: 94x60" (gain: 10.00)

Integration: 62.3 hours

Avg. Moon age: 13.19 days

Avg. Moon phase: 36.21%

Bortle Dark-Sky Scale: 8.00 job: 1810909

RA center: 94.881 degrees

DEC center: 55.610 degrees

Pixel scale: 0.913 arcsec/pixel

Orientation: 83.694 degrees

Field radius: 0.595 degrees

Data source: Backyard


I've had this target on my list since I first found out about it in February and it's been at the top of my list ever since. I knew it was faint, so HFG1/Abell6 served as a kind of practice run for this. But I was not prepared. This was excruciatingly difficult. Ha was only barely visible on 400 second subframes and OIII was only visible in stacks. Even now, I still don't think I got enough OIII signal, but I think the only way to improve on that would be darker skies or 3 nm filters, neither of which I have at the moment. Part of me wants to say "never again". The other part of me is thinking 'maybe if I had a really sensitive CCD, a Tak Epsilon, Hyperstar or RASA and a second mount...' (so I guess that does mean 'never again?'). This image marks the first time I've done anything with PixInisght, however, it was only noise reduction. It's still terribly noisy, though, but man is PixInsight difficult! At any rate, I guess this means I'm in the process of learning how to use PI now, so expect more revisions, especially since it's a lot noisier than I was hoping it would turn out. However, I'm still not sure I can extract anything else out of this. The OIII in particular was ridiculously weak.

Special thanks to Horst Ziegler, Frank Iwaszkiewicz and Bob Andrews who all gave me some invaluable pointers on this as well as J-P Metsavainio for sharing his tone mapping process, which made this possible. It never would have been published without it - tone mapping enabled me to really overstretch the OIII.



Chris Sullivan



Additional contrast enhancement, levels adjustment and noise reduction. Still not as clean as I'd like, but it's the best I can do at this stage. This will probably get a very thorough revision once I figure out PixInsight (like sometime in 2019???).


Someone mentioned that the background was "blotchy," so I looked to see if one of my previous revisions had a less blotchy background and used that instead. This had the added effect of reducing star sizes and halos.


I imaged the star field for a little over 1.5 hours with the refractor and one-shot color camera so that I could zoom out a little on this. I'm not 100% sure the blending is working - unsurprisingly, a lot more stars appear in 600 second subs than in 60 second subs...


I finally figured out a way to get the noise down to the level I wanted without destroying detail - only took me four months! This also enabled me to adjust the levels to where I wanted them.


I learned a better way of smoothing out the background while revising my Cat's Eye Nebula, so I wanted to apply that here. I also desaturated the stars a little and adjusted the levels to make it brighter.

Sky plot

Sky plot


PuWe1 (Purgathofer-Weinberger 1), 


        Chris Sullivan