It moves!

Nov. 9th, 2007 12:15 am
fivemack: (Default)
A squall-line came over this afternoon, down from the Orkneys on the wings of a tree-felling and ship-sinking wind, bringing behind it beautifully clear sky; Ed had said that he'd tried and failed to photograph the comet, so I wondered if it had faded substantially, and went out with a range of cameras.

With my little camera (Canon Powershot A510; 15s f/5.5, 140mm-equivalent, ISO 400) I get the left-hand picture. It's not a good picture - the lens is flaring badly around the brighter stars, and the colours are much too blue, with alpha Persei looking the actinic-blue of an O-type star when its spectral type is a more prosaic F5 - but it's a 200-gram pocket camera not intended for astronomy; the right-hand picture is with totally different kit but at about the same scale, taken by me on Saturday, to show that the comet is moving.

With a camera of inconvenient size (Nikon D100; 200mm, f/2.8, the camera and lens weighing in at 2.3kg, 4-second exposure at ISO 1000, push ISO up a couple of stops in gimp cursing at the lack of 16-bit-per-channel support) I get

So it's still pretty visible to me; I'm surprised that Ed couldn't get a picture of it without sky-fog issues (in that it's a lot brighter than sky-fog to me, and would be visible through it unless the exposure was so long that the sky-fog saturated), unless where he lives is a lot more floodlit than a central-Cambridge back garden.


Nov. 4th, 2007 12:36 am
fivemack: (Default)
As I came back from the Parkside ceilidh this evening, I noticed that the sky was clear, Comet Holmes visible to the naked eye as the corner of a triangle in Perseus which I knew wasn't there the last time I admired Perseus (the comet grew brighter by a factor 30,000 about ten days ago), and my brain not entirely befuddled. So I set up the most elaborate camera gear I had access to on a tripod in the garden, and got this:

I'm sure I can do better - I didn't set up the impressive telescope that [ profile] major_clanger lent me, because there was only one of me and it was midnight, and I've really done very little processing on the raw camera output. In particular, there are bright green stars in the photo above, and those don't exist. That picture is a few-second exposure at 80mm f/2.8 ISO1000 with my Absurd Photojournalist Lens; exposures at 200mm f/2.8 make it look bigger but not obviously better:

The geometry of this comet is a bit odd - basically we're between it and the Sun, so the tail is pointing directly away from us and visible only as the elongation of the coma.

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