Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) 0.64 arcsec / pixel.  The Zoomify image scale is 0.80 to 3.20 arcsec / pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ internal filter wheel, AstroDon Filters

Acquisition Data

8/10/2010 to 8/20/2010 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.  AOL guided

Exposure

Lum (no filter)  240 min (16 x 15 min, bin 1x1)

Ha                 480 min (16 x 30 min, bin 1x1)

RGB               270 min (  6 x 15 min each, bin 2x2)

Software

• CCDSoft, CCDStack, Photoshop CS w/ the Fits Liberator plugin, Noel Carboni's actions.

• eXcalibrator for (b-v), (v-r) color calibration, using 15 stars from the NOMAD1 database.  The lower image is corrected to compensate for galactic extinction.

• PixFix32 (pre-beta) to repair hot/cold pixels and column defects.

• CCDStack to calibrate, register, normalize, data reject, combine the sub exposures and LRGB color.

• PhotoShop for LLRGB plus Ha combine &  on-linear stretching.  The Ha data was added to the LLRGB's red channel, using the lighten option for opacity.

North is ~ to the top. The image is rotated 40° clockwise.

NGC 6946 is located just 10 million light-years away, behind a veil of foreground stars, in the constellation of Cepheus. During the 20th century, at least six supernovae, the death explosions of massive stars, were discovered in NGC 6946. The most recent nova was 2004et. This high frequency of supernovae is the reason for the Fireworks Galaxy nickname.

Because NGC 6946 is at low galactic latitude, we view it through a lot of dust and various nebulae. This causes the light to become reddish, just as the Sun is red at sunset. This effect is called Galactic Extinction.

This image was highly stretched, to show the foreground galactic clouds.