Re: ATM Alt Balance and Eyepieces

["Don Clement" <clement@san.rr.com>]

Hello Doug,

I would suggest using some sort of  mechanical toggle action so that the
solenoid is only on for a very short time. The solenoid would only act as a
trigger to change the mechanical state of the friction mechanism.
Alternatively, one could use two syringes tied together with tubing for a
hydraulic method that uses no battery power. Or even a cable system similar
to bicycle brakes. ( I just changed to V brakes on my MB)

Don Clement
San Diego/Running Springs

----- Original Message -----
From: "Doug Tanaka" <dtanaka@seanet.com>

I am wondering what other folks do to keep the optical tube on a
well-balanced Dob from rising up when removing a large eyepiece - like a
Nagler - to put in another eyepiece?  I adjust my balance using combinations
of bungee cord, but the loss of two-plus pounds invariably causes the tube
to rise and I lose whatever I was looking at.  My own solution to the
problem is to make a solenoid, mounted in the mirror box, that will push
opposing, rubber tipped rods through holes in the mirror box, applying
friction against the rocker box.  The solenoid will activate through a small
switch mounted next to the focuser.  Theoretically it works, but the
solenoid I made (thin 1/2" tubing, wrapped along 2-1/2" of its length with
150' of #26 magnet wire) gets pretty warm in a short amount of time - not a
good thing to have in the mirror box.  I am thinking about adding more wire
to increase resistance, (it's now about 6 ohms @ 12VDC), and this should
lower the heat some.  Short of putting in a heat shield, does anyone have
thoughts on how to reduce the heat without reducing magnetic strength?