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| IC 1848 and IC 1805: The "Heart and Soul" nebula... |
High overhead on winter’s evenings lies the constellation of Cassiopeia, an area of sky rich in star clusters and nebulae. A particularly large area of nebulosity lies on the Cassiopeia/Perseus border, the so-called “Heart and Soul” nebula (IC 1805 and IC 1848).
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| Stellarium map showing image field of view... |
In the late 1890’s, Barnard discovered IC 1805, describing it as “a cluster, considerably open, extremely large nebulosity extends following (to the east).” The star cluster he recorded (today usually referred to as Melotte 15) is that at the centre of the extended area of nebulosity that we today call IC 1805, although from his description there is no doubt that he also saw at least some of the surrounding glow.
Similarly, IC 1848 was discovered by Barnard at around the same time and was described as "a cluster, stars faint, extends …. to the east, in faint nebulosity." As with IC 1805, the entire nebula of IC 1848 has come to be regarded by the designation originally given to the star cluster and its immediate nebulosity.
The Heart and Soul complex are emission nebulae that form a vast star-forming complex that resides in the Perseus spiral arm of our Milky Way galaxy. The complex is 580 light-years across and comprises of giant bubbles of intensely hot, rarefied gases that are being blown into the dust surrounding the central cluster stars and rendered fluorescent by the intense radiation emitted by these hot young stars. These stars are less than a few million of years old; youngsters in comparison to stars like the sun, which is nearly 5 billion years old.
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| Annotated image showing designations of objects shown... |
The annotated image above shows the designations of some of the objects visible.
The Soul Nebula complex (IC 1848) is also designated by its
Sharpless catalogue number of Sh2-199. I have no idea what a “Soul” is supposed
to look like: some
Within the Soul Nebula is a small patch of bright nebulosity designated at IC 1871 (Lynds Bright Nebula 637), that itself contains a dark dust nebula sometimes referred to as the “Whirling Dervish” nebula (a name also given to NGC 3247 in the southern hemisphere). A small knot of nebulosity to the south of IC 1848 has been designated at Sh2-198, with a similar knot to the north designated as Sh2-196. Just to the south-west of Sh2-196, a group of three other tiny Sharpless nebulae can be seen, Sh2-193, Sh2-192 and Sh2-194. The bright star cluster NGC 1027 (discovered by Herschel in 1787) lies just to the south-west of these.
The Heart Nebula, IC 1805, is also designated as Sh2-190, which includes NGC 1795/NGC 896, an area of nebulosity referred to by some astrophotographers (with their usual lack of imagination) as the “Fish-head” nebula. The central cluster Melotte 15 is evidenced, with some of the associated dust columns. The small but bright star cluster Markarian 6 is visible on the south-western border of IC 1805.
Of particular interest are the two faint galaxies at the bottom of the above image, Maffei 1 and 2. These galaxies form part of a local galaxy group some 10 million light years away. Both were originally thought to be galactic nebulae, with Maffei 2 even being given a Sharpless designation (Sh2-195/197). Their light is heavily masked by dust lying in the galactic plane of our own galaxy, and they were only recognised in 1968 by infra-red observations.
In terms of my own imaging, the colour image was compiled from data obtained from narrowband Ha, SII and OIII images. The Ha signal is quite strong and indeed, was actually obtained through high haze without too much “noise” creeping in. Unfortunately, my polar alignment was a bit off and I had to manually stack the Ha images using an old AIP4Win programme (which can handle field rotation, unlike the version of Astroart that I normally use). This doesn’t let you remove hot pixels as part of the stacking process though, so some faint “streaks” can be seen in the final image if you look closely.
The SII and OIII signals are considerably fainter and required 2x2 binning.
I removed the stars from the narrowband channels using Starnet, then combined them as RGB (Ha/SII/OIII) in PSP7. This gave a rather greenish image, one that I corrected by over-laying a red mask of the Ha channel as a “colour” layer at around 20%.
The stars were added back in using unstretched narrow-band data as above, with a similar red correction.
A final overlay of the Ha data (stars reduced by the “erode” function in PSP) was added as a luminance layer to improve the detail in the nebulosity.
