Obscure target imaged with the JGT

2 January 2023

Aleks Scholz: "It was a long-time dream of mine to take this shot, a repetition of  the famous first epoch image taken 50 years ago with the JGT, in April 1962. But it is so much harder with today's technology, but here it is. Go outside and you might catch a glimpse of the Moon with your naked eyes."

Picture of the Moon taken with the James Gregory Telescope.

The Moon is not the most obvious target for a big telescope. Yet, in April 1962, upon completion of the James Gregory Telescope at the St Andrews Observatory, the Observatory Director at the time, Professor Walter Stibbs, took a shot of the gibbous Moon, for fun, and produced a beautiful image of the Earth's satellite against a dark background. While building the telescope took the better part of two decades, the exposure time for the Moon was exactly one second.

In 2022, the JGT celebrated its 60th birthday. It is still the largest Schmidt-Telescope in the world, and in good working order, but taking a picture of the Moon nowadays is slightly harder than 60 years ago.
While the picture in 1962 was taken with a photographic plate, the telescope is now equipped with a digital CCD camera. Only a few years ago we acquired a CCD that has the size to cover the area of the full moon entirely, giving us a chance to reproduce the 1962 shot. 
Due to the much increased sensitivity of  CCDs compared to photographic plate, we also had to put on strong 'sunglasses' – a filter that blocks out 99.9% of the light – to be able to point at the Moon. Again it took one second for the shot itself, but hours of preparation, not counting the months of waiting for the weather to be clear at the right time and moon phase. 

None of these two Moon pictures serves any scientific purpose - except demonstrating that the telescope is working fine. To our knowledge, the only published scientific work at the University Observatory that involves the Moon was the measurement of the size of the bright star Aldebaran, by monitoring its occultation by the Moon (Brown, Bunclark, Stapleton, Stewart; Monthly Notices of the Royal Astronomical Society, Vol. 187, 753-755 (1979)).