Here is Seattle we usually have few opportunities in winter to do deep sky astrophotography. Fortunately I still have some sets of unprocessed data which I saved from the summer months. This weekend I finally got around to processing one of the sets.
The image you see here is that of IC 1795. It is a star forming region near the much larger Heart Nebula, also known as IC 1805. This is a false-color composite of narrowband (HA, OIII, SII) images taken between 8/31/2011 and 9/8/2011. This particular arrangement of colors was originally used for Hubble space telescope photos and is therefore known as the Hubble Palette.
From the December 10th, 2009 APOD writeup on Don Goldman’s version of this image: “This colorful cosmic portrait features glowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. The nebula’s colors were created by adopting the Hubble false-color palette for mapping narrow emission from oxygen, hydrogen, and sulfur atoms to blue, green and red colors, and further blending the data with images of the region recorded through broadband filters. Not far on the sky from the famous Double Star Cluster in Perseus, IC 1795 is itself located next to IC 1805, the Heart Nebula, as part of a complex of star forming regions that lie at the edge of a large molecular cloud. Located just over 6,000 light-years away, the larger star forming complex sprawls along the Perseus spiral arm of our Milky Way Galaxy. At that distance, this picture would span about 70 light-years across IC 1795.”
As mentioned above, frames from this exposure were taken over multiple nights from 8/31/2011 to 9/8/2011. Each frame in the image consists of a 20 minute exposure, and there are 63 frames for a total of 21 hours of exposure time. Here are the details on the image capture:
19 exposures of HA taken between 8/31 – 9/1, with 20 minute subs each
30 exposures of OIII taken between 9/2 – 9/3 and 9/7 – 9/8 , with 20 minute subs each
14 exposures of SII, taken between 9/5 – 9/7, with 20 minute subs each