16 Apr 2018

Observatory Visit

When 21 members of RHYC and the CA gathered at the Orwell Park Observatory they already knew they would not be seeing any stars through the overcast skies. Instead Bill Barton of the Orwell Astronomical Soc explained to us all sorts of things we did not know about the history of the observatory and its telescopes. He told us that the it was built by Col Tomline as a vanity project. A one-time Commodore of RHYC and original developer of the Felixstowe Dock and Railway his family name was really Pretyman  but his grandfather who was already Bishop of Lincoln, tutor friend confidant and advisor to Pitt the Younger found he could inherit even more money by changing his name to Tomline. On the death of the Colonel the family name reverted to Pretyman who owned Orwell Park until forced to sell in the depression of the 1930s. They still live in the large house visible from the river upstream of Orwell Park and farm nearly 3000 acres around Nacton. Bill went on to introduce us to the various telescopes at which point your correspondent found himself grappling with his recollections of O level physics. He first showed us a refractory telescope which looked like everyone’s idea of a telescope but suffered from the fact that when light passes through glass the different wavelengths refract differently producing a “rainbow” effect around the image. He then showed us various reflecting telescopes that used mirrors rather than lenses and avoided the rainbow effect by placing the reflective surface in front of the glass rather than behind it, all cleverly though out by Isaac Newton. He also explained that for astronomical telescopes size matters rather than magnification. The bigger it is the more you can see. And that more important than the quality of the lens is the quality of the mounting to stop it shaking. There are modern computerised telescopes that you just point at the sky and after a few minutes communicating with satellites they will work out where they are and which star is which but Bill could clearly not see much fun in that. We then moved on to the Col Tomline’s wonderful piece of Victorian engineering. Bill explained that it was built to track, not vertically (elevation) and horizontally (azimuth) but at an angle aligned to the axis of the earth. This meant that when a star was tracked over a period of time it always presents the same aspect to the telescope. At this point your correspondent’s capacity for spatial awareness met its limits. Tonight however we were only tracking the goings on in Pin Mill so we all helped rotate the dome and peered through the telescope. Without the aid of a computer Bill informed us that the square of light we could see was a window in the Butt and Oyster. It was now 10 o’clock and Haley Dossor thanked Bill and his colleagues for a most informative evening.

David Pearce

Kathryn Deaton