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Comet 103P/Hartley, 2010 Sep - Nov


This comet was predicted to be at its brightest around 21 October 2010. Being high in the sky for UK observers until October it was not too difficult to find but it does require optical aid (camera, as here, or binoculars). I have not photographed it since mid-October but it may still be possible as it swings round towards Orion.

 2010 Nov 4

NASA's EPOXI spacecraft flew past this comet at a distance of 700km and took some amazing photos revealing it to be shaped like a skittle.


 2010 Oct 18

After nearly 2 weeks of cloudy nights I found the comet again, heading south-east in Auriga:

Comet 103P almost at its nearest to Earth

Canon EOS5DMkII 254mm Newtonian @1200mm f/4.8 30x15s ISO6400 2010-10-18 21:36:35-21:47:15 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)

The average length of the star trails is 80 pixels (in the original image, not the scaled version here). In this configuration the image scale is 3271 px/degree so the trails are 80 / 3271 = 0.0245 degrees long. The comet moved that far in time interval 10m40s = 640s. So the comet was moving at 86,400 x 0.0245 / 640 = 3.30 degrees per day.


 2010 Oct 6

The comet is moving towards the Perseus double cluster, h & χ Per. This picture was taken without a telescope. The camera was simply fixed on an undriven photographic tripod. You don't need an equatorial mount to do this!

Photo showing both comet 103P and the Perseus double cluster.

Canon EOS5DMkII 24-105mm lens @ 105mm f/4.0 64x10s ISO6400 2010-10-06 19:34:16-19:46:48 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

I have a taken a better photo of the double cluster.


 2010 Oct 1

The comet is now moving below Cassiopeia, near ζ Cas.

Comparison photo of comet 103P

Canon EOS5DMkII 254mm Newtonian f/4.8 32x30s ISO6400 2010-10-01 21:03:09-21:21:10 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)

Showing the comet position later

Canon EOS5DMkII 254mm Newtonian f/4.8
30s ISO6400 2010-10-01 22:53:58 UT

North is approximately at the top, east on the left.

The image above shows a comparison between two different ways of processing one set of 32 photos. All processing has been done in GRIP*. On the left the photos have been shifted so that the comet stays in one position and then accumulated. That gives a proper view of the comet. On the right the stars have been merged, so the comet moves slightly in front of them. That makes it easier to identify the stars.

The brightest star, just up and right from the comet, the only star showing diffraction spikes, is Tycho 3659 1253 1. Its V magnitude is 8.63. The brightest trail immediately to the right of the comet is Tycho 3659 1811 1, V magnitude 11.04. These identifications were done in GRIP again, by plotting a star chart around the predicted position of the comet.

The single frame on the right shows how far the comet had moved 1 hour and 33 minutes later.

As often happens, the comet is rather less bright than expected at present.

* Note about processing: the right hand image used the standard batch process in GRIP, "Astro combine into 1 image". The left hand image was made much more laboriously: segment stars in each image, point to the comet, note its (x, y) position, translate (shift) the image so the comet is always in the same place. After saving all the shifted images, use the accumulate batch process (quite quick). This has prompted me to write a more automated version, where you only have to click on the comet as each image is presented. A new version of GRIP with this process in it will be released soon (as of 6 Oct 2010).


 2010 Sep 9

I took the following photo from a rural site without a telescope but on a motorised mount (HEQ5). The comet is just faintly visible next to the star 2 Andromedae at the top right. 2 and 3 days later I managed to photograph it again but from light-polluted suburbs and with the camera only on a simple static tripod, so the photos are not worth showing but I have plotted the positions as white crosses on this first photo.

Comet Hartley on 9th September and subsequent positions

Canon EOS5DMkII 24-105mm lens @ 105mm 10x30s f/4.0 ISO6400 2010-09-09 21:36:12-21:41:58 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)

In fact I could not see the comet on this photo until I took the later 2 shots and extrapolated backwards for the likely position. Shown here is only a small 1:1 scale extract (1 pixel on screen = 1 pixel in camera) from the full 21-megapixel image on which GRIP detects more than 12,000 stars!

I hope to be showing better pictures here as the comet brightens.

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