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Thursday, March 24, 2016

A new image, the Lower's nebula

We now have had few clear nights after having a solid cloud cover for over two months. Transparency and seeing were poor at most of the time though. I managed to collect some data for two imaging projects. The Lower's Nebula was the first one. This is a dim and rarely imaged emission nebula in constellation Orion. There are not too many photos out of this one and it was difficult to collect information about it. Total exposure time is only 5h, I will continue this project at spring season 2017.

Lower's Nebula

The photo is in mapped colors from the light emitted by an ionized elements, 
red=sulfur, green=hydrogen and blue=oxygen.


The Sh2-261 (Sharpless 261), also known as the Lower's Nebula, is a faint region of doubly ionized hydrogen. Its apparent dimension is about 50 arcminutes in East-West direction and 30 arcminutes in North-South. So, it has an apparent size about twice the full Moon diameter. Of course the real size of the nebula is much larger! But we have no information about the distance of this hydrogen cloud, so we are not able to determine how large it is. (Source,

Technical details

Processing work flow

Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 21 iterations, added at 25% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Celestron Edge HD 1100 @ f7 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 x2 and SXV-AOL

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

Exposure times
H-alpha, 9 x 1200s =3h
O-III, 3 x 1200s binned = 1h
S-II,  3 x 1200s binned = 1h
Total 5h

A single uncropped, calibrated and stretched 20 min. H-alpha frame as it comes from the camera

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