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Sunday, 29 November 2009
Art stolen from the sky
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M33
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Monday, 23 November 2009
Nuisance lighting
Sun Dog
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A galaxy...in just 2 minutes
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Big scope peers into the depths of our spiral arms
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Abell 20 is a faint planetary nebula in Canis Minor near Monoceros, which is nearly as wide from our perspective as the beautiful Ring nebula in Lyra. The main difference is that this one is about magnitude 14.7, nearly 6 magnitudes fainter and only 1/200 th as bright! It needs a hefty telescope like our 20” to help gather and capture its elusive photons, most of which are a delightful turquoise shade of doubly-ionised oxygen. The central star looks quite busy but only appears so from our distant vantage point. It is magnitude 16.5. Apologies for what looks like green rain falling diagonally across the picture. It is an artefact of some detrailing I did and the over-processing required to see the “faint fuzzy”.
Gassy young stars
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This is me peering deeply into the Pleiades cluster. So deep, even with my field widener attachment, that I could only see two of the stars within the cluster. And this field is 40 arc minutes across. Now, obviously, this isn’t a properly deep picture, like you would see in some expensive CCD camera advert (that doesn’t give a price), or a magazine pic of the week. But to me it is deep, because it shows lots of blue clouds floating about between the stars, reflecting their spectrally blue cosmic light. It wasn’t a long, or particularly well tracked set of camera exposures, but it’s the subject I’m interested in, and my aim is to maximise the aesthetic appeal of the final picture. Contributing to that appeal is a particularly quirky set of flare lines coming off the star Alcyone at the left that provides a skewed detail to the picture. The streaky nebula at centre is named after the star, Merope which is only 30% as bright as Alcyone.
Messin' with filters
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Lumicon’s 1 ¼" UHC filter is a superb addition to my visual astronomy toolkit. I’ve seen the stringy, fluorescent shockwaves of the supernova remnant in Cygnus, the North America nebula, and now I have faintly seen the glow behind the horse head nebula. But for photography it is a bit disappointing. The light is mostly rejected - it seems to be too narrowband for good imaging and the light really should be collimated first for it to block the correct wavelengths. I can’t quite work out why the photographic result should be so different to the visual experience at the eyepiece. Any comments welcome. I did 5 exposures that tested the tracking of the 20” scope (60-90 seconds each). Detrailing, stacking and processing resulted in this faint but fairly decent picture of the Horse head nebula's Hydrogen Beta (H-β, λ = 486.1342 nm) emission.
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