The Stellar Halo of M31

500mm/F2.8 telescope
Nikon D800 (astro-modified)
3-frame mosaic
total exposure time = 29.3 hr
more flavors of this image and technical details in <a href="http://www.astrobin.com/221217/" rel="noreferrer nofollow">www.astrobin.com/221217/</a>