Re: Mark IV mount

[Chris Albertson <chris@topdog.pas1.logicon.com>]

Just a few more loosely related ideas...

I have made a couple of suggestions like Arne's but Tom seems to have 
settled most recently on the German equatorial mount.  I was a little 
surprised.  I agree with Arne that one mount per four scopes seems
simpler.  Half as many motors, control cards, power supplies, roll
off roofs, and on and on.  A lot however depends on the ratio of
"fours" to "twos".  If most systems are "twos" I see Tom's point.

I don't think keeping two mounts pointed at the same place is so hard.
First off it need not be exact.  Secondly, I assume the Mk IV system
will be able to reduce frames in real-time.  If so we will know to
within an arc second where a camera was pointing after the frame is
reduced.  This is better then running back to the limit stop and counting
steps.  We could even build a mount flexture model but I doubt we'll
need it.

What are the color bands for the "fours"?  I thought a back illuminated
CCD would be required to do more then tree colors.  Has this problem
been solved?

It seems that having a mount that can only hold two scopes means you
would never want a "triple".  If the mount could hold four scopes
a triple would become a reasonable option again.

I think the simplest possible mount is a long tube
or beam aligned with the Earth's axis  The center of the beam is bored
through for a short Dec axis.  This short dec axis connects two optical
tubes or two pairs of optical tubes.  I think (?) this is called an
English mount but we use two scopes rather then a scope and a counter
weight. 

A lot also depends on the style of construction.  If I where building
the system I would design it to use construction techniques I could do
myself.  I'd likely use thin sheet metal and rivets, aircraft style
or maybe wood using furniture or boat building technique.  A machinist,
I am sure would find a way to put his lathe or mill to use.

Another question is, "What is the cost of a commercial mount?".  Back
when the talk was about a barn door mount "build it yourself" was
clearly cheaper but is a scratch built German equatorial still cheaper
then an off the self mount?  I don't know.  It could also be that the
people at each of the proposed Mk IV sites would be able to provide a 
mount and pier.  

There is some advantage in site built vs. "supplied by Tom".  One of
them is that things like concrete and block become reasonable
construction materials.  It may be that this kind of "site preparation"
is within the means of each site



aah@nofs.navy.mil wrote:
> 
> I'm also in favor of a single mount with up to 4 cameras.  I could
> envision a square box to contain the 4 cameras that is then mounted in
> a fork.  The box side would be ~10" for the 4"/f4.0 cameras, so that
> should be a relatively simple mount (after all, Meade does it pretty
> cheaply!).  For two-camera systems, you just fill two tubes of the four,
> and put weights if necessary in the other two tubes for balance.
>   Having two separate mounts for the full-up 4 camera system is not
> as good a solution in my opinion.  It is harder to get the fields to
> line up, the tracking will be different, two piers will be needed
> instead of just one, and the wiring gets a little more complicated.
> Arne

-- 
--Chris Albertson

  chris@topdog.logicon.com                Voice:  626-351-0089  X127
  Logicon RDA, Pasadena California          Fax:  626-351-0699