Monday, November 9, 2009

Red Giant meets Red Nebula

Click on each image for a large view
IC1396 is cataloged as a star cluster embedded in a nebula. Right in the middle of the nebula, the star cluster is easy to see in binoculars, but in this long exposure photograph it is overpowered by the nebula. This is a very large nebula, about 2.5 degrees across (5 full moons would span across it), but it is very far way (2,450 light-years) and very hard to see visually.
The bright star at the top is one of the largest known red supergiants in the Milky Way. William Herschel described it as "a very fine deep garnet color" and is therefore commonly know as "Herschel's Garnet Star". So why is it yellow and not red in the picture? The main reason is that in long exposure images bright stars tend to get overexposed and loose their color. In this case yellow was the result. Astronomers who view this star through large telescoes see it more orange that red.
The bottom image was a very nice surprise! I wanted to create an image with legends pointing to the various known objects in the nebula, so I turned into in a black-and-white image. When I did this I tried using a red filter. The result was a much brighter nebula that constrasted nicely with all the dark dusty regions (5 of them are Barnard Dark Nebulae). On the right side is a dark globule known as the "Elephant's Trunk" and vdB142.
Technical Photo Info
Camera: Q453 CCD
Lens: 300mm f/4 L IS
Apeture Setting: f/4
Exposures: 9 X 10 minutes (90 minutes)
Darks: 2 darks to create dark pixel map
Flats: 0
Biases: 20
Mount: Celestron CGE
Guide Camera: CCD-Labe Q-Guider
Guidescope: 400mm Tasco refractor
Calibrated, Aligned and Stacked in Nebulosity
Final processing in Photoshop

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