Pulse-Width Modulation (PWM) circuit for illuminating finder scopes.
Click on any thumbnail for a larger picture.
Project components for illuminating the polar finder
scope on my Orion AstroView and SkyView Pro mounts. The "head" fits in
a mount's polar boresight hole. It also works in the EQ-6/Orion Atlas
mount and, with different heads, on a variety of finder scopes. The
duty cycle can be adjusted from 0 to 95% but I find that about 10% is
perfect for most uses.
From left to right: head mounted on an Orion AstroView, Orion SkyView Pro, and
Orion Atlas (aka EQ-6) mount. The Atlas mount has its own illuminator so
this is to show it'll work with an EQ-6 (same manufacturer: Synta).
Inside of the controller box. As you can see from the size of
the battery and other components, there's little unused space. If I had to
do it again I'd use a larger box. :-)
At the left is an LED soldered to a mini-phone jack which is the
key to this project's universality. Similar LED+jack assemblies can be
mounted in a variety of tubing [right picture] to fit nearly any finder
scope. The tubing can be surplused vacuum cleaner parts or plastic piping
from any hardware store.