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.

The Rosette Nebula (NGC 2237,8-46)

30 x 180 second subs through a 300mm telephoto lens (another boot sale purchase) of unclear (possibly Russian) make, using an SXV-H9 in 2x2 binned mode and a Astronomik hydrogen alpha filter. I took these during the evening of Feb 3rd. 2007.

The images were calibrated with a master flat but no darks (I applied a mild median filter to the raw subs instead) and then stacked in AIP4Win. I imported the stacked image into Paint Shop Pro and applied a mild "edge preserving smooth" to smooth out a bit of noise and give the monochrome below.

I couldn't resist messing about with layers and colour masks in PSP to give the false colour image above. Click on either image for a bigger version.

I alway think that images of this nebula conjure up a picture of a giant, ghastly skull, with the cluster NGC 2244 nestling in its right eye socket.

IC1396

2,200 light years away in Cepheus lies IC1396, a vast sprawl of faint nebulosity that occupies five moon diameters of sky as seen from Earth. I imaged this during the evening of Sept. 20th 2006, using the SXV-H9 through a 135mm Zeiss lens I picked up at a boot sale for £3.

22 X 4 minute subs were taken in 2x2 binned mode, and processed in API4Win. 16 flats/flat darks and 16 dark frames were used in calibration. The final stacked and calibrated frame was Gaussian stretched and Van Clittert deconvoluted using the API4Win default settings, to give the final monchrome image below. The top image is a "false colour" one put together in Paint Shop Pro, just because I can. I think I prefer the monochrome one (click on the images for larger views).

The formation called "The Elephant's Trunk", a curious column of bright and dark nebulosity, is clearly visible just right of centre (north is up, west is to the right). The bright star in the northeast part of the image is Mu Cephei, Herschel's "Garnet Star".