The picture above shows more detail of the Parkes Master Equatorial
drive system. The gold-coloured main hour angle gear-wheel can be
seen, but in this image the worm gear that drives it has been removed.
Behind it, the "backlash" wheel and worm gear are visible. The
"backlash" worm wheel is attached to the upper gear-wheel with
springs. The two wheels are each driven by a worm gear at the same
speed, however the spring tension between the two wheels eliminates
backlash in the drive train and ensures smooth movement across the sky
in both directions. During the repairs last week, four old worm gears
were replaced with new ones.