June 2, 2012

Crescent Nebula, NGC 6888, in Ha (June 1, 2012)


The moon was 90% full, but one can shoot H-alpha under the moon.  This is the Crescent Nebula, or at least the part made up of excited hydrogen (and perhaps nitrogen).  What you see here is essentially a large front of excited gas created by the movement of a bright, active star (the one at the center of the nebula) through a cloud of hydrogen.  The brighter part looks more like a crescent; the name matches visual observations.

Flats were taken with an Alnitak Flat-Man, which just arrived.  I used one of these two years ago and always thought it the perfect solution.  Last night's use persuades me I was right. This is also the first image I've taken with an H-alpha filter through the Orion 6IN.  And it's the first time I've stretched subs to 20 minutes.  I should have done 30 minutes, I think, and will try to with the OIII, or with more H-alpha, if I try to gather more data on this object.

Telescope: Orion 6" f/5 Imaging Newtonian and Astro-Tech Coma Corrector (eff. at f/5.5)
Camera and Exposure: 13x20' thru the SXVF-H9, Alnitak Flat-man flats
Filter: Astronomik 12nm Ha [+NII]
Guiding: SX Lodestar and SX OAG
Mount: Takahashi NJP
Software: Nebulosity, Maxim DL, Photoshop CS3
Location: The Woodlands, TX

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