Stellafane 2021

By Chris Predom

Started my trip in light rain, from Hamden to Springfield Vermont. Arriving at 3 p.m. to slightly overcast skies. Some areas were very wet due to the heavy rains they received on Tuesday. I camped at the pine tree area known as Bortle castle. Former member Paul Schuler and family were camped close by. Thursday evening started out with some clouds and slight haze, and later on improved. I took part in the Binocular Marathon and received my pin. It was nice to just look at the Milky Way as it slowly rotated overhead, finally calling it a day at 1 a.m.

Friday started with a trip to the spetrohelioscope on the historic original site. This was my first time viewing with this instrument, as it always seemed to break down the other times I arrived. There was a large prominence visible. This is a very unique instrument that uses rotating prisms, diffraction grating and slits, not counting the mirrors needed to get the image to the eyepiece. This is a old design that was described in one of the early telescope making books. What was interesting is that the grating projected the entire spectrum on the wall that was easy visible, including some absorption lines. By moving the grating the solar image can be displayed in one of it’s many color lines, by moving that
band into the mirrors to be reflected back to the eyepiece. The rotating prisms basically cause a scan across the slits. One prism is for the entering light path, the other after the grating deflects light just before it enters the eyepiece. Both prisms rotate in sync, and this is what displays the portion of Sun observed, by building the image, like scan lines of a television tube. This happens so fast that you see the Sun like you see a TV picture.