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Monday, November 5, 2018

Sharpless 157 in Cassiopeia

I originally shot data for this Sharpless catalog object as Spring season 2018. I noticed that, I haven't publish a visual spectrum image out of it yet. So here we go, Sh2-157 in visual spectrum from narrowband channels.The mixture I'm using gives a very realistic color scheme. 

Red color is mixed by emission of an ionized hydrogen and Sulfur, 80% of H-alpha and 20% of S-II.
Green color is from the emission of an ionized oxygen, 100% of O-III
Blue color is mixed from the emission of an ionized oxygen and hydrogen, 85% of O-III and 15% of H-alpha. (The emission of an ionized hydrogen is added to compensate other wise missing H-beta emission.)

A mapped color version can be seen here:

A two frame mosaic of the Sharpless 157 (Sh2-157)
Please, click for a large image

Natural color scheme from the emission of an ionized elements, H-a, S-II and O-III
The photo width is about one degree of sky. (The full Moon covers about 0,5 degrees of the sky.)

An experimental starless version
Please, click for a large image

Details of the actual nebula stands out better in this experimental starless version.

close up
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Sharpless 157

The night sky between the constellations Cassiopeia and Cepheus is rich with nebulae and star clusters. The nebulae visible in this image include Sharpless 157 and Lynd’s Bright Nebula 537. The star clusters include Markarian 50 and NGC 7510. The planetary Nebula PLN 110-0.1 (WeSb) can be seen at lower left.

Sharpless 157 is sometimes referred to as the Lobster Claw Nebula for obvious reasons. The bright spot at upper left quarter of this photo is Lynd’s Bright Nebula (LBN) 537. Also designated at Sh 2 – 157a, it is a ring nebula around the Wolf-Rayet star WR 157.

At the lower right quarter of the image lays open star cluster NGC 7510.

With labels
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An older wide field photo of the area
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The area of a new photo is marked as a white rectangle. The Bubble nebula can be seen as a bluish pearl, just half a degree North West from the Sharpless 157. 
This photo is shot at 2007 with a QHY 8, a cooled astro camera and the Baader narrowband filter set, H-a, S-II and O-III. Tokina AT-X 300mm camera lens @ f2.8

Technical details

Processing work flow

Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 33 iterations, added at 50% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Celestron Edge HD 1100 @ f10 with 0,7 focal reducer for Edge HD 1100 telescope

10-micron 1000

Cameras and filters
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x 2 and SXV-AOL

Astrodon filters,
5nm H-alpha 3nm S-II and 3nm O-III

Exposure times

H-alpha, 24 x 1200 s, binned 2x2 = 8 h
O-III, 10 x 1200 s, binned 4x4 = 3 h 20 min.
S-II, 9 x 1200 s. binned 4x4 = 3 h
Total 14 h 20 min

A single uncropped, calibrated and stretched 20 min. exposures as they come out from the camera.




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