click to returnGAERTNER 10" COELOSTAT
Be sure and see the spectrohelioscope page

There is a lot of confusion between a Coelostat and a Heliostat. A Coelostat is a two mirror system that follows the sun and reflects an image of the sun that does not rotate as the Sun moves. A Heliostat can be a one or a two mirror system. (A page with my Alvan Clark heliostat from the USNO Transit of Venus Expedition is here.) The biggest difference is that with the heliostat the image rotates as the Sun moves. This makes for some difficulty in photography. Visually, however, it makes very little or no difference -- unless you are sketching! Following are some pictures of my 10" Coelostat along with the interior cage that hangs from the ceiling. The cage contains two refractor type telescopes. One (76MM (about 3") F15)  had the cell and one of the lenses but the outer lens was broken. I managed to locate a Unitron lens which just fit the cell, and the focal length was also correct. The other one was missing the lenses and the cell. It was about a 2-1/4" F35. I found a 5-1/4" F15. It had some chipping on the edges, but that didn't matter to me as all I needed was the center 2-1/4". Pictures below should tell the story. So it should be a 2-1/4" F35, except the guy cutting it broke it and has never replaced it. I found a lens very close to what I need and am currently making a new cell for it. The smaller long focal length telescope is used to project an image onto a wall or the floor. The 3" is used to project an image to the two prism Spectroscope. If you move the two small refractors out of the way, the Sunlight (IT IS NOT AN IMAGE YET; ONLY PARALLEL SUNLIGHT) then goes to the Spectrohelioscope.


The following images were taken of the equipment in "as found" condition, before any cleanup or restoration. More pictures will be added after this project is completed.

picture of primary mirror on coelostat
This is the primary flat mirror holder.
The wheel on top is a large worm gear and drive system.

  picture of secondary mirror pier  
The pier with mounting for the secondary mirror.
This reflects sunlight downward through the roof and ceiling to the cage assembly, below.

picture of interior cage assembly with telescopes  
This cage assembly has two telescopes in it which are used to 1) project an image of the sun on a wall or floor, and 2) to make an image to project into the Spectroscope. These two telescopes may be moved out of the way in order to allow the 6" F50 lens to be swung into the path of the sunlight. Pages on each scope are here 3" scope  2-1/4"

picture of prism type spectroscope
You can see the two large prisms in this picture of the spectroscope.