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Sunday, February 20, 2011
Sh2-132, an emission nebula in Cepheus
Image is in HST-palette, (HST=Hubble Space Telescope) from the emission of ionized elements, R=Sulfur, G=Hydrogen and B=Oxygen. Star colors are mixed from the NB channels, Red=H-a, G=O-III and B= 85%O-III + 15%H-a.
Sharpless 132 is a very faint emission nebula, it locates at the border of Cepheus and Lacerta. Distance is about 10.000 light years. This image covers about 210' x 160', that's about 3,5 x 2,7 degrees. Resolution is 3,79 arc seconds/pixel.
In this final version, a strong O-III area is visible as a Blue color in both color palettes. There is some S-II in the area too but it's weak.
Natural color composition from the emission of ionized elements, R=80%Hydrogen+20%Sulfur, G=100%Oxygen and B=85%Oxygen+15%Hydrogen to compensate otherwise missing H-beta emission. This composition is very close to a visual spectrum.
With this image, I had my QHY9 and the Tokina AT-X 300mm f2.8 lens perfectly perpendicular to each others. Due that, the image is very sharp, there is no sharpening or star reduction methods used.
At f2.8, everything hast to be perfect, collimation, focus and orthogonality. The critical focus zone is only about 14 microns at this optical speed. If it's missed at all, the sharpness of the image collapse. At perfect focus, light ends up in a pixel, if focus is missed, even lightly, light will fall to all nine pixels, not just one!
The temperature compensating focuser, TCF-s, works as a heart of my DIY lens focusing system. It keeps focus perfect at all night when ambient temp. drops, typically 15 or more degrees up here. (Half a degree drop is enough to destroy the focus.) You can see my focusing device here:
An experimental starless version as an animation
The purpose, of this animated image, is to show the actual nebula complex under the dense star field .
Processing work flow:
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack.
Levels, curves and color combine in PS CS3.
Tokina AT-X 300mm f2.8 @ f2.8
Platform and guiding, Meade LX200 GPS 12" @ f5
Image Scale, 3,79 arc seconds/pixel
Baader H-alpha 7nm 12x1200s, binned 1x1
Baader O-III 8,5nm 12x600s, binned 2x2
Baader S-II 8nm 10x600s, binned 2x2