Are those unsatisfactory at high angles for you specimens commercial? Which ones?
It is rather straightforward, in principle, to locate the center of mass on the elevation/altitude axis, if one makes a fork or one armed fork, or nested forks or nested one-arm forks.
I have used Losmandy male and female Vixen pattern dovetail pairs, for fore-aft adjustability. I have added a stop or stops to prevent fore or aft spillout when loose. I have some Losmandy D size dovetails for a similar mount , to hold 40 or more pounds.
The Mitchell 35mm standard heads, from Mitchell, CECO, National Camera, Quick-Set, Vinten (!! $$$$$!!), Sachtler(!!$$$$!!), etc., for heavy studio TV cameras of yore, or sports broadcasting today ( good place to see them in action is broadcasts of tennis tournaments such as the recent one at Indian Wells, Calif. ) are unsatisfactory at, or will not reach without wedges, high angles such as 80 or 90 degrees, or 70 or 75. The elevation axis is well below the mass center of the load. Balancing, fore-aft motion, spring setting, friction setting are troublesome.
How does one get a yaw motion with those, to avoid the
Dobson Hole at or near the Zenith? Stack another axis on top, thus further adding to the imbalance around the elevation axis?
Think: Cygnus in August in the Northern Hemisphere.
I speak from experience , having tried various schemes with those heavy duty heads, to avoid building my own mounts, and to conveniently mate big heavy duty , to 400 pounds load, tripods. I explored Hollywood purveyors decades ago. Any body want some 16mm Mitchell heads? Perhaps now collector's items or as props for 30's, '40's, '50's production sets? I mounted two or three USN 20 x 120 straight view on those ( not simultaneously).
With a straight view binocular, chin and knee clearance, and neck fatigue, are problems at high angles, even with elevating central support columns.
Those are lesser, but substantial, problems with WW II 20 or 45 or 60 deg. inclined view specimens, at or near the zenith. Movie or video heads place the operator close to the support column or tripod legs, where interference/ fatigue at high angles is usually unavoidable without heavy and vibration susceptible counterweighting schemes
Edited by Gordon Rayner, 24 March 2016 - 12:29 AM.