October 2014 - Picture of the Month
NGC 6946 The Fireworks Galaxy in Cepheus
Image Courtesy of David Davies, Cambridge, UK. Please click on the image for the high resolution version.
For more images from David please visit his Flickr Photostream.
Last Thursday, 2 October, was a particular clear, cold night with reasonable transparency. A bright first quarter moon did, however, restrict what one could see.
I had a short-list of objects I could attempt to image in Cephus and Cygnus and settled on NGC 6946, The Fireworks Galaxy, Arp 29, Caldwell 12. This is my first view of this galaxy. We view it through plane of our own galaxy and it is significantly dimmed by the intervening stars and dust.
The data defining the spiral arms were only a few hundred ADUs above the bright sky background given by the moon. For a while I wondered if I would achieve a presentable image, especially when I discovered that the 100 minutes of luminance data I had gathered were spoiled by a finger print on the luminance filter. I must have been really clumsy when I changed the filter wheel in the camera.
So this image is essentially RGB only, comprising 45 minutes each of RGB in 5 minute subs. I constructed a luminance layer from the composite RGB image and separately processed that to make a final LRGB image.
- Telescope is a Skywatcher Quattro 254 mm F/4 Newtonian with a Tele Vue Parcorr.
- Camera is a QSI 583 with a Lodestar off axis guide camera guiding via PHD2.
- Mount is a Skywatcher NEQ6 controlled via EQMOD.
- Image capture was with Nebulosity.
- Automatic focussing was with Scopefocus working with Nebulosity. Image stacking was with Deep Sky Stacker and processing with Pixinsight and Photoshop.
This is a crop from the final image.