M20 - Trifid Nebula
From the author of Sizing Up The Universe
02:15 EDT Jun 17, 2006 and
21:44 EDT Aug 17, 2009.
Starlight Express SXV-H9 on Tak FSQ106 at f/5.
Hα=48+51 min, OIII = 36+81 min
(in guided 4-minute subexposures and unguided 3-minute exposures).
Limiting sky mag:
Hα=15.1, O-III = 13.9.
L = Hα +OIII, R= Hα, G = B = OIII.
Richardson-Lucy, Log stretch.