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Post by tmcewan on Oct 26, 2007 21:10:06 GMT
Posting this image on behalf of Bill Ward. Details: Glengarnock, Ayrshire, October 26-27, 20:34 UT. 50mm lens, 20secs f2.8 200ISO.
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Post by billw on Oct 29, 2007 12:27:52 GMT
Comet Holmes is putting on a good show. Top image was taken at 22.34UT 26/10/07, 1 second exposure, undriven with canon 350d @800 iso through 6in f3.6 reflector Visually I estimated mag +2.5. Bottom image was taken at 22.58UT 28/10/07 settings as above. Visually I thought it was very slightly fainter than the first night maybe ~+2.6 Difficult in the moon light though
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Post by billw on Oct 29, 2007 12:31:20 GMT
I forgot to add, in the top image the coma is around 190 arc secs across and in the bottom it's grown to over 360 arc secs (in 48 hours) For those with good eyes this might be visible as a tiny disc to the naked eye now.
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Post by tmcewan on Oct 29, 2007 12:54:12 GMT
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Post by billw on Nov 5, 2007 9:58:36 GMT
Hi, Anybody else out there been watching the comet!? On Saturday night despite high cloud the comet looked great. It's still bright at around mag +2.8 and its now nearly 15 arcmin in diameter. A perfect object for binoculars and small telescopes. cheers, Bill.
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Post by horstm on Nov 6, 2007 9:44:03 GMT
Around 2007-10-27.0 UT (Friday night) cloud gave way to a Moon halo. Next to it were Perseus an the comet. Since then I've mostly taken once per night untracked exposures at f=50mm, f/2.8, 20s and 5s resp. The weather in Edinburgh was mostly not stable and clear enough to warrant setting up tracking with a longer lens. Magnitudes (compared to 3.01 delta Persei) and coma diameters are 2007-10-27.0: 2.6mag, 2.5' (3 pixel); 2007-10-27.8: 2.5mag, 3' (4 pix); 2007-10-28.8: 2.6mag, 4' (5 pix); 2007-10-30.0: 2.6mag, 6'; 2007-11-03.9: 2.3mag, 12'; 2007-11-05.9: 2.8mag, 16'.
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Post by beatlesfab on Nov 7, 2007 20:21:50 GMT
Very good images captured here.
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Post by billw on Nov 9, 2007 9:57:37 GMT
Hello All, Here are a few numbers to think on... Using measurements taken from my images, between the 26 Oct and 28th Oct the coma was expanding at around 559 m/sec. Between 5 Nov and 8 Nov this had dropped a bit to a still fairly fast clip of 461m/sec. Last night the coma was 21 arc min (at mag +3.2) in diameter which means at a distance from Earth of 1.622 AU it is approx 1.25 million km across! This is getting up towards the same diameter as the sun. This is some outburst! cheers, Bill.
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Post by horstm on Nov 12, 2007 23:26:56 GMT
Some more magnitudes (compared to 3.01 delta Persei) and coma diameters: 2007-11-06.9: 3.0mag, 18'; 2007-11-08.8: 2.8mag, 22'; 2007-11-10.8: 2.9mag, 22'; 2007-11-11.8: 3.0mag, 26'. These data are from images with 50 mm focal length, stacks of 4 x 5 seconds. I've put a picture taken at 400 mm focal length at www.chiandh.me.uk/astro/comets/holmes.shtml
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Post by billw on Nov 13, 2007 9:53:52 GMT
As the coma continues to expand the brightness is now starting to fade. Took this image through a 102mm refractor, 15x30secs with 350D at iso800. cheers, Bill.
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Post by horstm on Nov 22, 2007 23:37:00 GMT
Finally another data point. Magnitude (compared to 3.01 delta Persei) and coma diameter: 2007-11-22.8: 2.9mag, 30'. From image with 50 mm focal length, stack of 16 x 5 seconds. The total brightness still seems to be unchanged. But (i) this is now spread over a wider area and (ii) it is less concentrated in the centre, where the surface brightness is down almost threefold from 11 days earlier. Hence I can't see it with the naked eye (from the city) and it is difficult even in binoculars.
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