NGC 2237 & 2244 - Rosette Nebula & star cluster
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The Rosette Nebula, telescopic view
Canon EOS 5D MkII ISO6400
SkyWatcher 254mm Newtonian, f = 1200mm, f/4.8
HEQ5 mount unguided, 41 x 64s = 43.7 minutes total exposure
2014 Mar 22 at 20:51:30-21:51:41 UT
From Rookhope 54.8
The Rosette Nebula is in the very indistinct constellation of Monoceros, following behind Orion. It has multiple NGC numbers for different parts of the nebula. Embedded within it is the star cluster NGC 2244, the stars of which have formed from the gas and dust of the nebula.
The nebula is a cloud of glowing gas about 5,000 light years away with some dust shapes visible within it. Note that this image was taken with an unmodified DSLR camera, for which the sensitivity to H-alpha is only about 50% of the rest of the visible spectrum, so it is less red than you may see in other photographs.
Conditions were not good for taking this photo. I had to keep pausing for clouds going over and at this time of year there is limited time available after dark before Monoceros sets. So I am quite delighted with this result.
The Rosette Nebula, wide field view
Canon EOS 5D MkII ISO6400
Canon 100-400mm lens at 400mm, f/5.6
HEQ5 mount unguided, 31 x 80s = 41.3 minutes total exposure
2014 Mar 23 at 20:15:22-21:04:40 UT
From Rookhope 54.8
This image is much less impressive than the previous version (above) but it shows what can be done without a telescope. Several nebulae, such as the Rosette, are too extensive to fit into a telescopic field of view so the alternatives are to build up a mosaic of several images or to use the wider field of view of a telephoto camera lens. The lens I used here is an expensive one, costing much more than my telescope, but it has a much flatter field of view and does not suffer from the optical aberration called coma which is inevitable in the Newtonian design of telescope.
The wider field of view makes errors in the drive of the mount less obvious so I was able to use 80 second exposures rather than 64 seconds, to compensate for the lens aperture being f/5.6 rather than the telescope's f/4.8.
I have had to overprocess the stars in order to bring up the nebula, so overall the result is less satisfactory.
Earlier attempts
Through telescope 2011 Jan 6
Canon EOS5DMkII 254mm Newtonian @ 1200mm 46 x 30s f/4.8 ISO6400 2011-01-06 21:23:40-21:51:13 UT
From Rookhope 54.8
NGC2237 is in the constellation of Monoceros, the unicorn, to the east of Orion. This is an emission nebula and an associated star cluster (NGC2244), about 5,000 light years away. Published photos of the nebula show it much more red. The redness comes from hydrogen (the alpha line in the spectrum) but that is beyond the wavelength range of my camera. My photos possibly show what objects might look like to the naked eye if they were bright enough.
Camera only 2011 Mar 1
The Rosette Nebula is one of those that is really too extensive to fit into a telescopic field of view. So this is an attempt to photograph it with camera only (on HEQ5 mount, driven but not guided):
Canon EOS5DMkII 100-400mm @ 400mm 49 x 30s f/5.6 ISO6400 2011-03-01 20:40:28-21:08:30 UT
From Rookhope 54.8
400mm on a full frame camera gives a field of view of 5.15 x 3.44° but this photo was cropped to about half that size before scaling down for this page.