ETX TECHNICAL TIPS Last updated: 12 July 2001

Solar Sighting Aid

Sent:	Thursday, June 28, 2001 21:08:39
From:	marv.sumner@juno.com (Marvin C. Sumner)
I read of folks having trouble finding the sun!  Yes, it is pretty
bright trying to sight along the OTA.  Well, my rig worked fine the
first time. Its a plywood "saddle" which rests atop the 'scope and has a
front sight and a rear "projector screen".  While pointed anywhere near
the sun, the shadow of the front sight falls onto the rear screen.  You
simply slew the OTA around 'till the shadow on the rear screen
superimposes over the penciled picture of the front sight.  The assembly
is made of 1/8th inch hobbyist's plywood, cut out with a coping saw and
assembled with small wood screws (but dowel pins and a little glue would
do as well).

I started by dowel-pinning two pieces of ply together and laying out a
circle to match the contour of the OTA and cutting the front and rear
members at the same time.  The top of the front piece was trimmed to
resemble a gun-sight and the rear was shaped to be a "movie screen".
Penciled reference lines were left on the pieces to assure alignment
later.  Rectangular fore-and-aft pieces keep the crosswise front and
rear parts aligned parallel.





It sits atop the ETX-125 (or whatever 'scope you cut the contours to
match) by gravity until the altitude gets too high, then a couple of
cup-hooks and a short bungee cord are needed.  Notice that it can also
serve as a piggy-back holder for batteries, TV transmitters, etc. (or
the interface box for the Cook-Book CCD I'm building).

This gadget was cut from hobbyist plywood & woodscrewed together; pretty
easy.  The only challenge is keeping the reference lines straight so
that the columniation matches the telescope barrel.   Notice the outline
of the front sight penciled onto the rear "screen".

Here it is attached to the ETX-125/EC





Now pointing near the sun with the shadow of the front sight near the
penciled image on the rear screen.





Pointing at this high angle shows that cup-hooks and a short bungee will
be needed to keep it all nested onto OTA.  This last view shows only
that the shadow of the front sight is visible near the penciled outline
on the rear screen.  It also shows the need for a bungee tie-down when
at high altitude.

I forgot to mention, in the pix of the SunSight that the box blocks off
the view of the Finder Scope - a safety feature when admiring sunspots.

Marv Sumner

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