Every photograph of the original GMT shows its telescope tube, the lower part being sheet metal and the longer, upper part comprised of a criss-cross lattice of metal strips. This design was intended to save weight and reduce wind drag in the upper part of the tube.
After the telescope was moved to Mt Stromlo, the lattice tube was unbolted from the boiler plate lower part and cut into two pieces. The lower lattice part was strengthened by the addition of inner rings attached to the original metal strips, then outer rings were added to hold new sheet metal, which fully enclosed it. The upper lattice part was less fortunate – it was left outside and exposed to the flames of the 1953 bushfire at Mt Stromlo, after which it was dumped.
We estimate that we can use the original lower lattice more-or-less as-is but without the sheet metal cladding. The new, upper lattice will be designed to suit whatever secondary mirror and other apparatus it will need to hold in place.
This is an extract from our newsletter Phoenix Newsletter – Issue 3, November 2009 (PDF 597KB).