ASTROPHOTOGRAPHY TIPS/TECHNIQUES Last updated: 10 October 2004

Subject:	Homebrew, low profile, top end counterweight instructions
Sent:	Friday, October 8, 2004 12:21:22
From:	Neumann, Eric M. (emneumann@tva.gov)
I wrote you a few days ago about this and I'm finally getting around to
writing it up and sending pictures, hope you like it.

I've really enjoy your site and it has greatly increased my enjoyment of
my ETX-90.  I hope you are on Meade's payroll, or at least get lots of
perks from them

Clear skies, 
 Eric 



Here is a simple and cheap method to make a primary end counterweight
for any Schmidt or Maksutov telescope, just adjust the procedure to suit
your particular needs.  These instructions are specific to my camera and
Meade ETX-90 EC Telescope.

I'm using my trusty Pentax K1000 camera body and Meade's standard
t-tube.  I used a digital balance and actually weighed the force that
the camera was putting on the OTA when level (the alt axis lock must be
free).  I then weighed a measured short piece of #8 bare copper wire and
determined a weight per foot for the wire.  I also measured the moment
arm for the camera as mounted ont the scope (the distance from the alt
axis to the back of the camera * weight as measured)and using the length
from the alt axis to the front end of the OTA to find that I needed
about 15 feet of #8 wire.

I then wound the wire around a piece of 3" PVC pipe in a very tight
coil.  I actually drilled a hole big enough to poke the wire into to
hole the wire while winding.   The coil springs out when you let go and
is almost big enough to go around the OTA.  I then trimmed the bent end
off of the coil.  Then I slipped the coil up and over the end of the OTA
one turn at a time.  After I had about 1 or 1 1/4 inches of coil pushed
onto the end of the OTA, I rewound the rest of the coil over itself to
keep it reasonably short.  Finally, I wrapped the coil with black
electrical tape to hold it together.

The weight is compact and holds itself tightly to the OTA and my scope
is balanced to within a couple of ounces with the Pentax attached.   The
copper is soft and although leaves copper colored marks on the front
lens cell they rub off easily enough.  Installation and removal requires
a slight twisting motion in the direction that expands the coil.

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