IC1805 & IC1848

Back in December last year, I set out to make a wide-field image of this area in Cassiopeia, to include both of these spectacular nebulae in one frame. I've only just got around to working them up (click on any of them below to enlarge).

The SXV-H9 camera on a 135mm camera lens gives a 3.5 by 2.5 degree field, allowing wide-field imaging with quite modest equipment. Mosaicing frames allow even wider field images to be assembled. Images above and below are stacks of 30 x 300 second frames of the adjacent nebulae in Cassiopeia, IC 1805 and IC1848, taken on consecutive nights. Exposures were 2 x 2 binned and taken in H-alpha. The binning was needed to get the exposure time down as I wasn't guiding, but it doesn't seem to have affected the resolution too badly.

After stacking and stretching in AIP4Win, I imported the separate images as layers into a Paint Shop Pro image frame that was large enough to contain both frames. I used the "eye dropper" tool to measure the brightness of each frame and adjusted the brightness and contrast of the images so that the grey background of each image had the same value. I try and aim for RGB values of 10-15 in the darkest parts of monochrome images. I then rotated the IC 1805 ("Heart Nebula") image until corresponding stars could be overlapped in each frame and then "selected" the IC 1805 area with a "feather" of about 15 pixels, pasting it onto the IC 1848 frame. The images were slid about until the stars overlapped (I change the top layer to "exclusion" mode so that star images vanish when perfectly aligned, and then restore to "normal" when a match is obtained) and then the layers were merged and cropped to give the final wide field pair as below.

Whilst these images can never match those taken with big-chip CCDs and wide-field apos, I still think their quality is still quite reasonable.