re:SV: ATM re:Eq. platforms

["Howard Banich" <Howard.Banich@nike.com>]

Nils,

Thanks for your response to my plea - although I know better, sometimes it 
seems I'm the only one with a platform. 

I too use a threaded rod, but driven by a synchronous motor. The platform 
has a square base, and uses the cylindrical design formally made by Tom 
Osypowski. In fact, if you've ever seen his original commercial design 
(from 1990) you'll have a very good idea what my platform is like. He's 
moved on to a triangular base, conical design that uses direct roller 
drive powered by steppers.

I haven't tried photography with my setup either, but I'm confident if I 
ever do get the bug for imaging I'd get pleasing results. For now I'm 
having too much fun collecting photons first hand.

Howard
Portland, Oregon

----------------------[Reply - Original Message]----------------------

Sent by:"Nils Olof Carlin" <nilsolof.carlin@swipnet.se>
 Howard,

> ps - hey list, doesn't ANY one else out there have a platform?

I built my first version and got it running a year ago.

To match the simplicity of a Dob would be hard indeed, but I'd say for
visual use, it needn't be very much more difficult to make - it does
need a motor and drive
electrics/electronics.
A late version for a 30 lbs 10" Dob weighs about 6 lbs, this includes
about 2 lbs of 6 "D" cells! It is triangular, with largest dimension
about 15", and a total height of 4" which is not very much more than
the ground board it replaces. Here I used a Poncet approach, with a
small ball joint and 2 pieces of Teflon sliding on Formica (designed
for 60 deg N!!) for movement - this bit is indeed simpler than even a
Dobsonian mount.
For driving it, I use a threaded rod driven by a stepper motor from a 5
1/4" disk drive, with a simple 555/SAAA1027 circuit (similar circuits
can be found on the net). After 1 hr of tracking, it takes 2 minutes to
automatically reset itself.

Admittedly my design is not for photo, but it is fine for visual use -
very few Dobs are designed for photo anyway. 
The platform has its limitations, but I think it deserves to be made by
many more of us. And I too believe photo accuracy is obtainable if you
try a little harder (I haven't yet - but I suspect I don't have the
mentality of a true astro-photographer anyway ;-) 


Nils Olof




=====================================================================