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Medusa Nebula / Abell 21 / Sh2-274

Technical card

Resolution: 4500x3250

Dates:Dec. 8, 2018Dec. 11, 2018Dec. 19, 2018Dec. 20, 2018Dec. 27, 2018Jan. 4, 2019Jan. 7, 2019Jan. 11, 2019Jan. 12, 2019Jan. 15, 2019Jan. 16, 2019Jan. 22, 2019Jan. 26, 2019Jan. 27, 2019Jan. 29, 2019

Blue: 100x150" (gain: 139.00)
Green: 74x150" (gain: 139.00)
ZWO H-alpha 7nm: 129x300" (gain: 139.00)
ZWO OIII: 165x300" (gain: 139.00)
ZWO Red: 72x150" (gain: 139.00)

Integration: 34.8 hours

Avg. Moon age: 12.61 days

Avg. Moon phase: 47.65%

Bortle Dark-Sky Scale: 7.50 job: 2543730

Locations: Home Roof (Bortle 7-8 / Est. Sky Quality: 18.53), Springfield, PA, United States

Data source: Backyard


I had a little mishap with my flockboard during capture that caused a few issues, most of which I just cropped out, but it still left me with some strange star colors. Special thanks to Jarrett Trezzo for pointing out exactly what the main issue was there - I fixed it as much as possible. I had trouble bringing out the fainter strands of hydrogen and oxygen, but at least I got something there. I'm satisfied overall, but there's room for improvement. Maybe I'll come back one day?



Chris Sullivan
License: None (All rights reserved)



Desaturated the cyan and yellow in the background.


Medusa Nebula / Abell 21 / Sh2-274, 


            Chris Sullivan