homemade remote control for Canon EOS 300D/Rebel etc

The Canon EOS DSLR 300D/Rebel and 10D are limited to a max exposure of
30sec before Bulb for longer exposures is invoked ideally via a remote
control release to avoid vibration.

The Canon version is expensive. My homemade version [converted old
'scope hand-controller] with 4m lead retains full control of auto
focus/exposure in regular photography, is posted at

http://home.freeuk.com/m.gavin/digsky4.htm

with link to circuit etc.