RE: [APML] Observatory - the Mounting

["Chris Schur" <cschur@cybertrails.com>]

Geoff, my tangent arm is a 3/8 threaded rod driven by the 3 inch spur gear.
A dc motor has a small 1/2 inch spur on it to make it turn.  So the
reduction is great.  The mounting was originally designed to carry a heavy
fork, but later I added the dec head instead, and made it into a german
equatorial.  It should drive the schmidt or any thing up to about 200
pounds.  Another point of interest is the use of 60hz synchronous motors for
the Ra drive.  Im tired of fighting the stepper motor vibrations that have
plagued my AP1200 mount, and ruined more than a few ccd images.  The ST4
will change the frequency of my drive corrector to 40 to 80 hz.

Chris

-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of astropix@att.net
Sent: Sunday, October 27, 2002 8:43 PM
To: astro-photo@seds.org
Subject: Re: [APML] Observatory Progress - the Final image.


 Chris...

     Congratulations on the successful completion of your observatory...
like
many others on this list and elsewhere... I look forward to viewing the
results!

     I examined the mounting closely, as I'm building a rather large GEM
myself
and I wanted to see how you addressed certain issues. I like the idea of
having
the DEC motor drive assembly fixed to the main DEC surface plate... my
preliminary DEC drive/tangent arm plans attached the drive motor to the OTA
main saddle plate. This would mean the DEC motor itself would rotate
parallel
with the OTA... your set-up doesn't let the motor mounting move in DEC...
only
with RA. Your arrangement also puts the DEC brake at the bottom of the DEC
axis... my plan would have put the DEC brake at the top, just underneath the
OTA. How does balance work out with your set-up? Seems that it wouldn't be
so
top heavy in DEC balance... but what about RA?

     I noticed as well the comparatively small drive gears on the DEC
drive...
aren't those spur gears? This disparity in gear sizes is encouraging to
me... I
was beginning to think I might have made too much compromise in my own gear
size selections, which were somewhat cost/availability mandated. I have
decided
against a tangent arm DEC assembly, and will go with a clutched worm drive
on
both RA and DEC. I have my gears... the DEC gear can be viewed
here --------->

     http://home.att.net/~astropix/12_inch_Byers_gear.html

and my most expensive single investment in this hobby to date... the RA
monster

     http://home.att.net/~astropix/18_Byers_gear.html

     I'm sure you have thoroughly tested your mount... the work on your web-
site clearly indicates you know what you're doing! You have utilized a lot
of
wood... strong but light weight and low-cost... clever, eh? Let us know when
this stuff sees 'first light'!

 Congrats again...

 Geoff Powers


 PS... (the structure itself is awesome... not mention :::location::: !!!)






> Hi all, This weekend, we finished our observatory project by intalling the
8
> inch schmidt camera.  Now the fun begins, shooting the fall and winter
skies
> from a extremely dark sky site.  I hope the next postings youll hear from
> this instrument will be rich full colored imagery!  Heres the final shot:
>
> http://www.PSIAZ.com/Schur/astro/clrckoty-final.html
>
>
> Take Care,
>
> Chris
> Astro:  http://www.psiaz.com/schur/astro/index.html
>

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