1. Surveying transits had an attachment known as Roelof's solar prism which formed four overlapping images of the sun. Observations were made on the small diamond-shaped shadow in the center.
2. I conjecture that the plain sights used by the Danish astronomer Tycho Brahe and later by Hevelius were based upon equal brightness. They would have to be adapted to the sun, vs. stars. For stars, observations approaching 15 arcseconds (about 1 second of time) would seem possible optically. 3. Use of a lens to project an image of the sun should permit observations to a small fraction of the solar diameter. Gordon -- | XII | Gordon T. Uber, 3790 El Camino Real, Suite 142 | XI | Palo Alto, CA 94306-3314, email: [EMAIL PROTECTED] | X \ /| CLOCKS and TIME: http://www.ubr.com/clocks/ | IX \ / | Reynen & Uber WebDesign: http://www.ubr.com/rey&ubr
