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Contains:  13.03, 24 phi Aur, 93 Minerva, IC 417, IC417, NGC 1931, NGC1931, Sh2-234, Sh2-237, The star φAur
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The Spider & Fly Nebula - IC417 & NGC1931 - Ha(HaR)GB, 


            Kurt Zeppetello
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The Spider & Fly Nebula - IC417 & NGC1931 - Ha(HaR)GB

Technical card

Dates:Jan. 21, 2020Jan. 22, 2020Jan. 24, 2020

ZWO B 1.25" optimized for ASI1600: 34x90" (gain: 139.00) -20C bin 1x1
ZWO G 1.25" optimized for ASI1600: 37x90" (gain: 139.00) -20C bin 1x1
ZWO Ha 7nm 1.25": 92x180" (gain: 139.00) -20C bin 1x1
ZWO R 1.25" optimized for ASI1600: 41x90" (gain: 139.00) -20C bin 1x1

Integration: 7.4 hours

Darks: ~12

Flats: ~15

Bias: ~20

Avg. Moon age: 27.53 days

Avg. Moon phase: 5.98%

Bortle Dark-Sky Scale: 5.00

Temperature: -4.00 job: 3227946

RA center: 5h 29' 26"

DEC center: +34° 25' 53"

Pixel scale: 1.205 arcsec/pixel

Orientation: -11.415 degrees

Field radius: 0.954 degrees

Resolution: 4526x3465

Locations: Happy Frog Observatory, Monroe, Connecticut, United States

Data source: Backyard


This colorful area of space rich in hydrogen and oxygen gas is located constellation Auriga. Along with other nearby space oddities such as the open star cluster M38, emission nebula IC410 with Tadpoles and the Flaming Star Nebula, the Spider Nebula - IC417 and the Fly Nebula - NGC1931 make for a wonderful place to image. I am not quit sure I see a spider or a fly but nevertheless, it is gorgeous. The emission nebula (Spider) contains an open cluster consisting of hot young stars and is about 100 ly across and 10,000 ly away. The Fly is both an emission and reflection nebula but only about 10 ly across.

Processing had its usual weirdness. This is the third time I had trouble stacking narrowband data in PI. This time it was the Hydrogen alpha subframes. It stacked everything but the Ha stacked image looked like a negative or something - it has happened on the last two sulfur images I did and though it was limited to just that. The RGB stacked nicely. Oh well, fortunately DSS worked like a charm.

I made a combined layer for the red channel (50% Ha - 50% red) rather than straight Ha as it just looked better and then added Ha as a luminosity layer (70%) to make the final image. I really wanted to keep the Ha nebulosity but also wanted to keep it somewhat natural so I had to do a lot of balancing. Göran Nilsson posted a really good version of the Spider and Fly on Astrobin Link to Image recently which convinced me to image this. I also did not crop it much at all (what a surprise) as I like faint Ha regions that are visible on the outer edges.



Kurt Zeppetello
License: None (All rights reserved)

Sky plot

Sky plot


The Spider & Fly Nebula - IC417 & NGC1931 - Ha(HaR)GB, 


            Kurt Zeppetello

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Imaged with APT
Northeast Imagers