I haven't tried to measure the variation of sub-tended arc of the Sun's
disk but have read (URL below) of it being done for the Moon, an approx.
14% variation. However, with an enlarged solar image, via a Heliostat,
perhaps the 3% variation (mentioned below) could be be teased out.
Hmmmm...http://www.fourmilab.ch/earthview/moon_ap_per.html -Luke Jeff Adkins wrote: > > It is true, however, that the difference is observable in page-size > photographs that > lie side by side on a table. There is an old project physics activity that > has the > student plot the distance to the sun based on changes in the apparent size of > the > sun; and from this data you can computer the shape of the earth's elliptical > orbit > to some degree of accuracy. You can also get the perihelion and aphelion > distances > and dates from this sort of data. > > Jeff Adkins > > "Richard M. Koolish" wrote: > > > >From the web page: > > >http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/SEgeometry.html > > > > "Eclipse geometry is complicated by the fact that Earth's orbit around the > > Sun > > is elliptical. As a result, the Sun's apparent semi-diameter varies from 944 > > arc-seconds at aphelion to 976 arc-seconds at perihelion. This 3% range in > > apparent size is, of course, quite indistinguishable to the naked eye."
