Thursday 25 March 2010

Siamese Twins

The Siamese Twins are a pair of overlapping and presumably interacting galaxies aka NGC 4567 & 8. Their magnitudes are approx. 11.7 and 12.1 and they are quite small, 4.6 & 3.1 arcminutes (respectively), because of their large distance of 120 million light years from Earth.
The pulses sent to the stepper motors that drive our 20" scope had just been adjusted to attempt to cut the wobbly, vibrating tracking, so I gave it a test on these fine objects. I did manage to get one reasonably steady 2-minute exposure, but on closer inspection there were slight star trails, in addition to the field rotation limiting the exposure. But overall it was no better, I'm afraid. I had to detrail most of the 30-second images that made up this final image, but a pleasing result nevertheless with a total exposure of 5 minutes at f/3 ish, with quite a misty sky just before moonset. Also in this image at top is NGC 4565 - a 12.0m, 3.2' galaxy and at bottom, IC 3578 - a 15.1m, 0.9', tiny splash of light.

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