ATM Wooden equatorial mount in TM#24

[Eric Allen <ericallen@worldnet.att.net>]

Patrick Abbott wrote:
> 
> pabbott@compusmart.ab.ca
> Hello
(snip)
> Are you the same Eric Allen who wrote the fascinating article on the
> construction of a wooden equatorial mount in Telescope Making #24?
> As I am thinking of building a similar mount ,I thought I would find 
> any bugs the builder found before I start.I will make enough mistakes of my
> own anyway!
> Thanks
> Pat
> Patrick Abbott
> Leduc
> Alberta
> Canada
Hi Pat.
Yep. That's me.  Thanks for the kind words.  Dobs were still new at the
time, and I tried to incorporate the good features of the Dob into an
equatorial.  Right off, gravity stops working for you and starts working
against you.  But it can be done.  Pound for pound, the equatorial will
never be quite as simple or as solid as the Dob, but you can come pretty
close.  There are several things to keep in mind.  Forks work well with
fast scopes, but not so good for slower scopes.  You have to either
build them excessively large, or you have to add weight to the mirror
end of the tube, unless the tube assy is already heavy on that end.  
I sold the mount years ago (retaining the optics) and built a Dob which
weighs 150 lbs.; about 100 less than the mount in TM.  I never drove the
TM mount.  At the time, I didn't really need an equatorial; I was just
experimenting.  If I were building it again, I would go lighter, except
for a permanent installation.  The lighter you can make the tube assy,
the lighter you can make everything else.  The wooden tube was heavy.  I
would now go with something much lighter, like thin wall PVC, which I
currently have in the Dob.  Open framework tubes are light, but I prefer
solid tubes.  I would put the polar disc on ball races (much easier to
find than ball bearing casters) with a teflon brake if necessary for
friction.  A 1/8" strip of stainless steel around the polar disc would
be better than aluminum.  At your latitude, you could make the polar
disc continuous.  I had to cut mine for access to the southern sky.  I
would probably now use hardwood plywood.
I am using more magnification than I used to, so I am again thinking of
making an equatorial mount.  This time I plan to make an all aluminum
double yoke.  (I have better tools now than I did then.)  This is still
in the planning/dreaming stage.  
Good luck.  If this doesn't turn out to be your ultimate mount, you will
at least have learned a great deal about mounts in the process.  Hope
this helps.  If you have any more questions, ask away.
Eric Allen
ericallen@worldnet.att.net
Edmond, OK, USA
P.S.  My apologies to those on the list who haven't seen TM #24 and
don't know what the heck I'm talking about.