1959y1 19600427 0258 hridley

This image was taken on 1960 April 27 by Harold Ridley and Mike Hendrie at Reggie Waterfield's observatory. The following report is from JBAA vol 70, No. 7 (1960 September):

You should really be hearing from Dr Waterfield now, but as he has had to be away for a fortnight he has very kindly arranged for Mr Ridley and myself to observe the comet from his observatory at Ascot. Before he left he obtained a photograph of the comet on the morning of April 23, but the sky was so poor that we could barely see the comet with the naked eye. However, this 14-minute exposure did show the tail over two degrees long.

The next morning when Mr Ridley and I made two exposures of 21 and 44 minutes duration, the sky was still far from suitable for comet photography. Despite this the second plate shows the narrow tail nearly 8 degrees long and the head some 15 minutes of arc in diameter. The first slide made from this photograph shows about five degrees of tail, the remainder being too faint for reproduction.

After two cloudy nights it was unexpectedly clear on the night of April 26-27 when we secured another three plates in varying conditions. However, the last exposure of 70 minutes duration made just before twilight intervened this morning, was taken in good conditions with a sky that was both transparent and steady. The second slide now on the screen was made from this photograph. The tail on the negative extends to the edge of the plate, more than 10 degrees, and the coma is 25 minutes of arc across. The narrow tail can be seen on the slide: it is, I think, unusually narrow. It is nearly but not perfectly straight, and broadens out a little some three degrees from the head.

These photographs were all taken with Dr Waterfield's 6-inch 7/4-4 Cooke lens of about 26 inches focal length using whole plates. Kodak Oa-O bluesensitive plates were used. Owing to the comet's very rapid apparent motion, the guide-star had to be shifted relative to the micrometer's cross-wires every 15 seconds, during which interval the comet had moved through 6-65 seconds of arc. This was the greatest degree of trailing permissible if sharp photographs were to be obtained. The comet was too large and ill-defined to enable guiding to be done on the comet itself.

The original negatives show signs of a central condensation elongated along a line at right angles to the axis of the tail. This cannot be seen on the slide because the head has been over-exposed to show the tail, but I believe that Mr Alcock also noticed this and has a drawing that shows the same effect.

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