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Wednesday, January 17, 2018

Sharpless 157 (Sh2-157) in visual colors

We have had only two clear nights, January 7. and 8., at this month. I shot exposures for this target at both nights.

I have publish a mapped color version out of Sharpless 157 at January 14. This new version shows the target in visual spectrum. Ionized hydrogen (H-alpha) and sulfur (S-II) are emitting red light, ionized oxygen (O-III) emits bluish light. This is a kind of difficult target due to large intensity variations and low surface brightness.

Sharpless 157 (Sh2-157)
Please, click for a large image

Image is in Natural color palette from the emission of ionized elements, R=Hydrogen + Sulphur, G=Oxygen and B=Oxygen + 10% Hydrogen to compensate the missing H-beta emission. A mapped color version can be seen HERE.

A closeup
Please, click for a large image


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.

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.

An older wide field photo of the area
Please, click for a large image

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 astrocamera and the Baader narrowband filter set, H-a, S-II and O-III

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, 12 x 1200 s, binned 2x2 = 4 h
O-III, 10 x 1200 s, binned 4x4 = 3 h 20 min.
S-II, 9 x 1200 s. binned 4x4 = 3 h
Total 10 h 20 min

A single uncropped, calibrated and stretched 20 min. exposures, for H-alpha, S-II and O-III emissions, as they come out from the camera.




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