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Refractor Collimation

Started by David Simons, 09/28/2004 10:16PM
Posted 09/28/2004 10:16PM | Edited 09/29/2004 12:04AM Opening Post
I finally got a chance to assemble my surplus 11" triplet lens that came off an aircraft simulation system (see bottom picture)into a tube with a focuser. The lens is reasonably square inside the tube now, but has a very short focal length of 35". I have stopped the lens down to 10", but this still gives a very steep f3.5 light cone. I looked at the moon first, and although the center of the image was sharp, the edges were a little soft. One side of the moon was reddish, while the other was greenish blue. I think I have some alignment/collimation issues. Just for fun I pointed the scope at Vega. Wow, the color on each side of the slightly elongated brilliant star was reminiscent of something you might see in the 60's. I then checked out Cassiopeia, and even with a lot of moon, many stars were visible in the 1.88 degree FOV I was using. Although the alignment is off, I think for low power viewing, the scope shows a lot of promise.

Since the lens almost fit snug inside the 12" aluminum tube I already had, I mounted it inside the tube using a set of rings to hold it in place. (white rings in the picture). But now unfortunately do not have a way to adjust the lens as the internal rings are fixed!

The focuser, however, can be moved laterally, and also tilted by adding shims. Maybe I can collimate from the focuser end only?

Anybody have some thoughts on how to collimate this beast ?

David Simons

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David Simons