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Friday, April 3, 2015

NGC 1491



I shot the data for this dim object at 16. March but the processing of it ready now. I found this as a difficult target due to a very low surface brightness of the surrounding nebula. The central part is bright and it makes difficult to balance image nicely.

NGC 1491
Click for a large image

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.


A wider field version
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INFO

NGC 1491 is an emission nebula at the constellation Perseus. The distance from the Earth is about 11.000 light years. In the bright area, at a center of the photo, a strong stellar wind from a star BD +50 ° 886 is blowing the gas away. The radiation from the same star makes the gas glow by ionizing elements in the nebula.


Image in mapped colors
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Image is in mapped colors from an emission of  the ionized elements. Golden areas are from emission of sulfur and hydrogen, S-II and H-alpha, blueish areas are from ionized oxygen, O-III.


A wider field version in mapped colors
Click for a large image



Image in light of an ionized hydrogen, H-alpha, only

This B&W photo show the emission of H-alpha only


Orientation in an older wide field photo of the area

An area of the new photo is marked as a white rectangle. The wide field photo is taken at February 5, 2012 with a Canon EF 200mm f1.8 camera lens, QHY9 camera and narrowband filters. More info about this picture can be seen HERE



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 @ f7 with 0,7 focal reducer for Edge HD 1100 telescope

Mount
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, 15 x 1200s = 5h
O-III, 6 x 1200s binned 4x4 = 2h min.
S-II, 6 x 1200s  binned 4x4 = 2h min.
Total 9h

A single un cropped, calibrated and stretched 20 min. H-alpha frame as it comes from the camera
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Not much can be seen in this single 20min. exposure of the emission of hydrogen, H-alpha.



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