NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Working Analemma
From: Lu Abel
Date: 2006 Nov 05, 16:51 -0800
From: Lu Abel
Date: 2006 Nov 05, 16:51 -0800
FrankReedCT@aol.com wrote: > One of the lecturers at the Seaport Planetarium at Mystic Seaport back > in the late 70s painted an analemma on his living room ceiling. He had a > mirror mounted on a little base on the windowsill of a south-facing > window. Once a week at exactly noon local mean time, barring clouds, he > would mark the spot on the ceiling where the Sun's image was projected > by the mirror. After a year he filled in an arc connecting the points. > Sure enough, he had that classic "figure eight" analemma shape (although > as Herbert Prinz has explained, it probably shouldn't be called an > analemma). Not sure I remember Herbert's post, but I assume it was because the shape was distorted? At UPS, the figure-eight is severely distorted because the mirror from which the sun's light is projected is only 15 feet away from the wall and 5 feet above the top of the "analemma." The distance from the projecting mirror to the bottom of the analemma is over twice the distance from the mirror to the top of the analemma, leading to a significant distortion of its shape. The UPS "analemma" is a stainless steel path about 2 inches wide, inscribed at about 10 day intervals. It was constructed based on a set of plans provided by a professor who had to very carefully calculate the distortions induced by the location of the mirror. Although it hasn't been in service for a full year, I hear it's doing fine so far.... Anyway, it was neat to walk into a building and say "hey, I recognize that" when 99 out of 100 people on the street (and even well-educated college students) probably couldn't. Lu Lu Abel --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---