Re: ATM Important, very important

[Dwight Elvey <elvey@hal.com>]

Asaf Shtull-Trauring <astropal@yahoo.com> wrote:
---snip---
> 
> I just tried to check the balance of my mirror box on the rocker box,
> and damn it, it's not balanced when I try to look 45 degrees up to the
> sky... What should I do????????????

Hi Asaf
 There are two elements of balance that you need to get
right. First is end to end of the telescope tube and the
other, less sensitive one, is front to back of the tube.
 Put the tube down flat, horizontal, and balance it with some
weight such that a nudge will cause the same movement up or
down. If you can move the trunnions along the tube, it
is better than adding weights but adding weights will
be OK also. Start with bags of sand rather than iron
weights until you finish the dynamic balance. Put one
bag on the top of the light end and one bag under the
light end. These should be located where you expect
to mount your final weights. This isn't absolutely necessary
but it saves having to calculate the effective moments
of each weight. Use baggies and tape usually is the easiest
way to do it. At first, fill just the one bag until
balanced. Then split the sand, 50/50 into each bag to get close
to dynamic balance.
 Now point the tube straight up. Test the balance the
same way, by nudging and seeing which way it is off. Move
the sand from from the heavy side to the light side.
When you are done, you can weigh the bags to decide
how much weight to add. In the unlikely case that you
can't balance enough by moving all the weight, you'll need
to slightly modify how to position your weights.
Take the empty bag and move it to the same side of
the telescope as the full one but mount it right between
the two trunnions. Now fill this, with additional sand, until
balance is reached. Since this place would be balanced over
the trunnion when horizontal, it won't effect the first
balance.
 Your permanent weights can be most anything that you
can attach. Some even use bags with zippers. Some
use barbell weights. Another would be a piece of
pipe with end caps. One could then add lead shot
to bring it to balance. Use some imagination.
Orion sells some sliding weights that slide on
bars. To achieve good balance, you'd need one on
each side of the telescope. Look at Orion's, they are
called EZ Balance. They come in 1 and 2.5 pound weights.
A little expensive but look at them anyway.
They are mainly intended to be used to fine tune.
 If this isn't clear, I'll try to draw some pictures
and post them on my web site.
 Make sure to have dust covers removed, I forgot this
and had to add a 10 pound weight!
Dwight