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Tuesday, March 19, 2013

Sharpless 261, the "Lower's Nebula"

This starts to be my final images for this season. We'll be out of an astronomical darkness in couple of weeks, up here 65N. 
Difficult target just above the Orion, I have spent three night trying to collect enough photons to have a nice image. Sh2-261 doesn't rise very high up here, so I have only around three hours per night to shoot this.
I manged to collect five hours of H-a light and six hours UHCs-filtered colors. 11h total exposure time is not too much for this object.

Sharpless 261 (Sh2-261) , the Lower's Nebula

Image is in visual spectrum and dominated by the red light emitted by ionized Hydrogen, H-alpha. Blueish hues are from ionized Oxygen, O-III. Colors are shot simultaneously with H-a emission by using QHY8 color camera, Tokina AT-X 300mm f2.8 camera lens and Baader UHCs-filter.


SH2-261, or Lower's Nebula, is a Hydrogen Alpha emission region  located in the upper area of Orion, near the Gemini constellation. Image covers about a same area as a full Moon. There is  no information about the distance of this hydrogen cloud, so we are not able to determine how large it is.

The nebula is named after amateur astronomers Harold Lower and his son Charles, who discovered this nebula in 1939 from a picture taken with their homemade 8 inch, f/1 Schmidt camera.

Image in Hydrogen alpha light alone

Technical details

Processing work flow:
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Levels, curves and color combine in PS CS3.

Optics, Meade LX200 GPS 12" @ f5
Camera, QHY9
Guiding, SXV-AO, an active optics unit, and Lodestar guide camera 7Hz
Image Scale, ~0,8 arc-seconds/pixel
15 x 1200s exposures for the H-alpha, emission of ionized Hydrogen = 5h
Color exposures with QHY8 single shot color camera
36x600s exposures with UHC-sfilter = 6h

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