Re: [ATM] Unique New Equatorial Platform Design

[creator <creator@subarcsec.com>]

Greetings Mel!

 > >  > Ok, found the same mount in an old Telescope Making magazine,
 > >  > where it was called the box or corner equatorial mount.
 > >
 > > Could you please send me the reference and/or a copy of the article?
 > > I would very much like to examine the mount presented in that article
 > > and compare it in detail with what I have designed.

I would still welcome reference info, if possible, thanks.

 > Also from geometric first principles, the circle is perfectly
 > symmetrical in its plane when rotated about its center, as is
 > the line when rotated along its length...

This is correct if you are speaking of a "Platonic ideal" circle.
For an ATM to actually [achieve] a circle symmetrical enough to
produce tracking smoothness measured in arc-seconds... THAT is
more difficult. Also very difficult in practice is actually
implementing an axis of rotation for that circle that is
precisely perpendicular to its plane. :)

 > Concrete examples of the circle appear in professional (Isaac
 > Newton polar disk mount) as well as amateur (Rob Adam's tilt-a-dob),
 > and the well known Dobsonian. Incidentally, Rob, a true mechanical
 > talent, considered the circle and its perfect symmetry superior to
 > the rotating line because he found circle mounts easier to build.

"Easy to build" is a good and valid motivation! :) A better one
is "easy to build" plus "precision results".

 > In your case, the line is formed from the opposing vertices of
 > a cube.

That is one possible way of visualizing it. Based on your limited
descriptions, I can imagine the similarity of my device to the
"box or corner" mounts, but I would still very much like to
actually see one.

 > Combinations of both line and circle abound, for instance,
 > the Horseshoe mounting and professional altaz mounts that
 > use a vertically aligned zenith cone.  Combinations of
 > circles occur in alt-alt mounts as well as 5 pt equatorial
 > tables.  These circle combinations work because they use
 > translational symmetry.

My design is, of course, none of the above combinations. My
observation would be that in order for translational symmetry to
provide [useful] results, the circles you implement must be very
precisely machined, not an "easy" target for an ATM. And as mentioned,
when you combine circles and lines, there is also considerable
difficulty achieving accurate relationships among them.

BTW, I googled "siderostat" (thank you!) and while I see some vague
similarities to my design, I see no identity. The same is true
for the English or Yoke design.

 > Combinations of lines cannot occur as they are not continuously
 > symmetrical when translated.

I'm not sure what you are driving at here, and would welcome
any further exposition. :)

 > Making claims that lines are [innately] superior to circles
 > will cause a lot of ancients to rise from their grave <smile>
 > besides raising eyebrows of mathematicians and geometers who
 > understand group theory and symmetry.

Please don't misunderstand my claims. :) A line is not [innately]
superior to a circle; however, it may well be [implementationally]
superior to a circle. The garage ATM in many cases does not have
professional machine tools at his disposal. However, by mounting
and manipulating readily available and inexpensive artifacts
(i.e. chrome steel bearing balls) to define a single line, a polar
axis, the ATM can very inexpensively achieve phenomenal results
as described at http://subarcsec.com ... and the last thing I would
expect from my claims would be to raise the dead... :)

 > The equatorial table and variants that were built over a
 > several year period of popularity I referred to earlier were
 > based on a cube supported at opposite vertices and cut away
 > providing a flat level platform to place a 2-axis mount.

Thank you for this additional verbal description; it helps me
to visualize this a little better, but I would love to see a
photo or two or read a description from someone who actually
built one of these. Anyone of you out there? :)

 > Since you are making the claims I suspect that you will want
 > to conduct your own research as part of due diligence.

Yes I do, but in conjunction with my own research (which is
necessarily limited in access to resources, time, and scope),
I would humbly request and welcome specific references, articles,
pointers to good venues for such research, web sites, etc. etc.

The specifics of the cube-based corner mounts you mention that
I would most like to evaluate are these:

* How the vertices are supported
* Location of the center of gravity
* Drive mechanisms
* Quality of tracking achieved

Anyone having access to any such information or suggestions
as to where I might find it would do me a great kindness by
passing it along, thanks! :)

Once again, Mel, I appreciate your comments and interaction!

Regards,

-Dann
================================================================
Dann McCreary http://flyinghouse.com    creator-at-subarcsec.com
SubArcSecond Tracking Accuracy!  --   Visit http://subarcsec.com
Read The Bills Act http://www.downsizedc.org/read_the_laws.shtml
================================================================
"The heavens are telling of the glory of God;  and their expanse
  is declaring the work of His hands"  -     Psalm 19:1    (NASB)
================================================================ 


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