File:IC1805 -- H-alpha + RGB.jpg

Subject: IC1805 -- Heart Nebula (RGB + H-alpha)

Image FOV = 2 degrees 55 minutes by 2 degrees (175 minutes by 120 minutes)

Image Scale = 7.5 arc-second/pixel

Location: near Halcottsville, NY

Exposure: 26 x 10 minutes H-alpha plus 13 x 10 minutes RGB = 6h30m total exposure, ISO800, f/4.8

Filter: Baader 7nm H-alpha filter (H-alpha), IDAS LP filter (RGB)

Camera: Hutech-modified Canon 30D

Telescope: SV80S 80mm f/6 + TV TRF-2008 0.8X reducer/flattener = 384mm FL, f/4.8

Mount: Astro-Physics AP900

Guiding: ST-402 autoguider and SV66 guidescope. MaximDL autoguiding software using 6-second guide exposures

Processing: Raw conversion and calibration with ImagesPlus (dark and bias frames only, no flat frames); Aligning and combing with Registar; Levels adjustment on RGB and H-alpha image. Then: Red channel = 1/3 * RGB_ red + 2/3 * max(gamma(RGB_red, .75), Ha_red) Green channel = 1/3 * RGB_ green + 2/3 * max(gamma(RGB_green, .75), 1/3 * Ha_red/5) Blue channel = 1/3 * RGB_ blue + 2/3 * max(gamma(RGB_blue, .75), 1/3 * Ha_red/5) Then, more levels, cropping/resizing, JPEG conversion with Photoshop CS.