Well it’s been a miserable few weeks weatherwise, so time to write up some observations I’ve not got around to yet.
I thought I’d take a diversion from some of the Messier catalogue of objects I’ve been tracking down. So, looking through the star chart I thought this seemed a likely looking candidate, NGC 7023, otherwise known as the Iris Nebula, in the Cepheus constellation. From my site it sits in the slightly darker northern sky and is reasonably high at the moment.
NGC 7023 is a reflection nebula – a cloud of dust that is lit by reflecting the light of nearby stars. They tend to be blue, since the blue part of the spectrum is scattered more effectively than red. Other examples of reflection nebulae are those in the Pleiades, where nebulae can clearly be seen illuminated by the nearby stars.
What I particularly like about this image is what can’t be seen. There are clear dark areas around the nebula, where no background stars can be seen. I imagine that this is thick dust from the nebula blocking out starlight, but two far away from the central star to be reflecting any starlight of its own.
The image is a composite of 23 x 2 minute exposures, taken in two groups, with dark frames associated with each group.
