North America Nebula

Sigma 500mm/F4 @ F4
Nikon D800 (astro-modified)
STC Astro Duo Narrowband filter
total exposure time = 4.1 hr

more technical details in <a href="http://www.astrobin.com/418552/?nc=user" rel="noreferrer nofollow">www.astrobin.com/418552/?nc=user</a>