ETX TECHNICAL TIPS Last updated: 10 May 2002

Remote electric focus for ETX 70AT

Sent:	Thursday, May 9, 2002 9:27:53
From:	r_shoesmith@madasafish.com (Richard Shoesmith)
Having been frustrated by the lack of an electric focus for the ETX 70 I
have built my own. I know it doesnt look elegant, but it is very
effective and only cost about 32.00.

The basis for the focuser is the LEGO  9v motor kit which comes with a
useful selection of gears etc and the control /power box. The motor
which has a quoted rpm of 350 is geared down to approx 12 rpm or roughly
one turn every 5 seconds. Power is supplied by six AA batteries held in
the LEGO control box which has forward and reverse buttons. A fifteen
meter extension, patched into the power supply cable, gives the reach to
enable focusing to be controlled from indoors by the PC when using the
electronic eyepiece.

Photo 1 shows the gear assembly and photo 2, the method of attachment to
the scope using the dust cover for the T-mount to hold in place a thin
plywood support.

Richard

PS My next project is to power the scope itself. I have an 18v 1000ma
power adaptor going spare. Is this suitable?

Mike here: See the Telescope Tech Tip page for lots on Power Supplies.

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