WAITING FOR THE
Astronomical Observing and Photography
The binocular objective is held between a piece of 50mm PVC drain pipe and a 50mm join coupling
which also acts as a lens hood. On a very dewy night, another piece of 50 mm PVC can be inserted in
the front side of the coupling to act as a dew cone or extended lens hood.
The length of the tube is governed by whether you want the finder to be a straight through or a right
angle finder. A binocular prism can be used as a right angle finder. You can re-use the binocular eyepiece
but I find that a cheap GSO or Skywatcher plossl eyepiece is much better than the binocular eyepiece
The adjustment bracket has 6 x M3 threads tapped straight into the 75mm PVC pipe. You need to tighten
with care to avoid stripping the threads. I have been using this one for 4 years without issue. If you prefer
something sturdier, you can use steel thread inserts available at any hardware straight in the 75mm PVC.
I did machine the focus tube from aluminium. It should be possible to find step down PVC adaptors that
can act as a defacto focuser.
The foot is a piece of 25 x 50mm aluminium U-channel extrusion. The dovetail foot is cut with a hand
mitre saw from a piece of delrin, but with the light weight of the finder a piece of hardwood - maple or
ash would suffice. A standard finder bracket has a 2 x 60 degree mitre 1.25 inch (31.75mm) on the base.