In order for the dome to be as small as
possible and also so eyepiece height changes as little as possible
the alt bearings are midway along the telescope tube. This makes the
telescope very bottom heavy. The counter weight needed was 8kg at
the top of the tube. This was archived by casting a lead ring. I
received lots of advice on lead casting from the ATM list.
Possibilities offered included molding lead shot in epoxy resin.
The method I went with was described by Pete
Brooks . I bought the lead from a local scrap metal merchant. It had
been used for roofing. A plywood mould was made and the lead melted
in 4 lots using a coal/wood fire then poured in to the mould, It
took a fair bit of heat to melt 8kg of lead but the casting went
pretty smoothly. The resulting ring has a few bubbles in it but
still does the job.