I started building this telescope in
1986 when SEKAS held telescope-making classes at St Edmonds school in Dover. These
meetings where headed by John Underdown (SEKAS Instruments Advisor at the time) and Alan
Buckman (SEKAS Chairman at the time) . There were about 12 members making telescopes in
the class, hand grinding and figuring primary mirrors ranging between 4 and 10inch.
Most of which made from 1.5 inch Duran 50, which is a low expansion glass. Mine however is
made from 1 inch Plate glass. The arduous task of grinding the mirror started off
with the hogging out of the glass by using grade 80 carborundum until the mirror was
nearly down to the required radius of curvature and then working my way down through the
finer grits until finally reaching grade 600 carborundum. having worked my way
towards a spherical mirror through out the grinding stages it was now time to make sure
that the mirror was a perfect spheroid and having reached that goal, at last the
grinding stage was over. And it was now time to prepare for the polishing stage by making
a pitch lap. When it came to polishing the mirror I started off using
cerium oxide as the polishing agent. I spent what seamed to be an eternity polish the
mirror week after week but the cerium oxide seemed to be having little effect. At this
point John Underdown suggested that I give Tin Oxide a try. and it was not long
before I could see that the Tin Oxide was working. it was only a
short time before the mirror was completely Polished.
Next came the task of figuring the mirror to achieve a Palaboloid this was
achieved by changing the stroke used . within just one session the mirror was figured.
When tested all of the weeks of hard work involved was rewarded as with
John and Alan's help I had achieved a figure of 1/12 wave. A very satisfying conclusion to
a very enjoyable task.
Due to other commitments I had to shelve the building of the telescope for a while, not
picking the task back up until late 1989 and completing the telescope in early 1990.
