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Friday, March 29, 2013

Owl nebula, Messier 97

This seems to be my last image for the winter season 2013.

M97, the Owl nebula
in constellation Ursa Major

Click for a large image.
Image is in visual spectrum, red light is emitted by an ionized Hydrogen, H-alpha. Blueish hues are from ionized Oxygen, O-III. Some of the colors, like stars, are shot simultaneously with H-a emission by using QHY8 color camera, Tokina AT-X 300mm f2.8 camera lens and Baader UHCs-filter.


In my image the outer shell of ionized Oxygen, O-III, can be seen around the round nebula. It's very rarely imaged, I found just couple of images, taken with large 2-3 meter telescopes, showing it. I did use my "Tone Mapping" technique to dig out this very faint signal.

The Owl Nebula, M97, is located about 2,600 light-years away toward the bottom of the Big Dipper's bowl. M97, from Messier's list of objects, its round shape along with the placement of two large, dark "eyes" do suggest the face of a staring owl. One of the fainter objects in Messier's catalog, the Owl Nebula is a planetary nebula, a dying sun-like star as it runs out of nuclear fuel. In fact, the Owl Nebula offers an example of the fate of our Sun as it runs out of fuel in another 5 billion years. The nebula spans over 2 light-years.

A drawing of Owl Nebula from 1848

I wanted to place this sympathetic image here, It's a drawing of Owl nebula by William Parson back from 1848.

O-III channel processing
to show the outer shell structure

Click to see large image
  1. Calibrated and stretched stack, 8h of exposures.
  2. Stars are removed by using several iterations of "dust and scratches" filter under PhotoShop.
  3. Levels are set.
  4. First iteration of curves.
  5. Second iteration of curves, second set of "dust and scratches" filtering to remove background unevenness, mild gaussian blur and some median filtering (5x5) to reduce noise level
  6. Finally image number 5 is combined with second image from top to have both, core details and the outer halo.

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 4Hz
Image Scale, ~0,8 arc-seconds/pixel

Exposures from three different nights, 16., 26. and 29.03 2013

H-alpha 18x1200s, binned 1x1 = 6h 
O-III  24x1200s, binned 1x1 = 8h
Color exposures with QHY8 single shot color camera and Tokina AT-X 300mm f2.8 lens.
36x600s exposures with UHCs-filter = 6h

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