RE: ATM 5 hour straight bolt camera platform

[Anthony Stillman <atmer@flash.net>]

Mel wrote:
>...S&T article...tangent arm drives with... French curved arms
>...from the '80's, I think.


Yes, but this was a tangent arm.  Doug, as Donald put it, is describing a
sine arm.  It provides a far more accurate approximation from the get go,
hence adjustment curves won't need to be as extream

Its clear that some form of guide will be needed.  And, this can pull
double duty by holding down the board as well.  A dowel could be glued to
the end of the slide and allowed to move in opposing slots which bracket
the board.  Just the curve of the dowel may improve the accurcy.

Off hand I think the curve of a bent board would be trancendental, but I'm
not sure.  I also think a circular segment may be good enough.  I figure if
the tracking error can be reduce to 1 arcsecond over a few hours, that's
good enough.

Its going to take a few days for me to think through this, even with modern
pharmaceuticals (actually only because of), if others would do the same I
know I would appreciate it.  I'll post some more math toward the end of
next week (I hope)

Anthony

PS  Thanks again Doug for describing the Kniffen Drive.  I wish I had
thought of it.