SNR 111.7-02.1
This is 12 x 10 min exposures taken of Cas A with a new Astrodon NIR luminance filter that blocks all UV and Visible light, and passes NIR light past 700 nm with very high throughput. ST10XME self-guided on a 12.5" RCOS RC at f/9 in my suburban backyard (18.8 mag/sqarcsec). Seeing was a ~2.2". 12 x 10 min unbinned exposures. I have added RGB color with Astrodon E-Series filters with a balanced G2V star white-point. I have used a screen clipped layer mask and added in the strong NIR signal from the 700-800 nm NIR1 filter, blending it into the red color channel
A good starting point to read about Cas A is at:
http://www.seds.org/~spider/spider/Vars/casA.html
http://heritage.stsci.edu/2002/15/ Hubble Image
http://www.noao.edu/outreach/aop/observers/cassA.html NOAO from 20" RC
Cas A is a supernova remnant some 10,000 light years away and 10 light years across. It was likely observed by John Flamsteed in 1680, but was not recognized as a SNR. It is quite close, but not very bright, being obscured by interstellar matter, which makes it a good NIR imaging target, like the Maffei galaxies. It shows up strongly in X-Ray studies. There is a neutron star from the collapsed remains of the stellar core. Studies have found evidence of heavier elements, such as silicon and iron. It is located at RA 23h 23.4m DEC 58d 50m