One of the more unusual telescope designs at the 12th annual Weekend Under the Stars (also known as WUTS) astronomy gathering August 8, 9 and 10 at Foxpark, Wyoming, was this open-designed schiefspiegler (German for "leaning mirror") telescope. It was designed and built with an unusual external structure of kite struts by Longmont Astronomical Society (Colorado) member Tim Brown. It looks kind of like a tinker toy telescope, but it is a very efficient "folded optics" design, sort of like a Schmidt-Cassegrain, but with a much longer focal length, better contrast, and no center obstruction. It works best at high magnifications, Brown said, and is an excellent instrument for planetary and solar observations.

Tim writes, "This scope looks like a Buchroeder tri-schiefspiegler, but it is not exactly so. In the standard tri-schief, the tertiary mirror has a very weak spherical figure, and must reflect the light through a particular angle in order to correct the astigmatism introduced by the earlier off-axis reflections. In my scope, I borrow an idea from the Yolo off-axis designs, and correct this astigmatism by warping the secondary mirror into a slightly toroidal shape, using a mechanical spring assembly on the back of the convex secondary. This means the tertiary mirror can be flat, and can be at whatever angle I want, in order to put the eyepiece in a convenient place. Also, I didn't have to make that long-focus sphere."

Tim Brown's schiefspiegler: Light enters from the top of the structure to the main mirror in the box at the bottom of the scope. Light bounces back to the top of the scope to the secondary mirror (which is offset, leaving the light path to the primary mirror unobstructed), which bounces the light back to the third mirror on the right, which bounces the light back to the left, through the center baffle, to the eyepiece on the left side of the scope. (Photo by Gary Garzone)

Here's a closup view of the primary mirror, bottom, third mirror, right, and the eyepiece (the black one), left. Another mirror and eyepiece can also be seen on the left, but they are actually not as close to the black eyepiece as they appear to be in this photo. The other mirror and eyepiece are lined up several inches off to the side of the primary light path of the telescope. The extra eyepiece, diagonal mirror, and drum-like-object to the left of the main scope are all parts of the finder scope, which is a 3-inch f/6 Newtonian. The drum is the main mirror cell, with a cover on it. Tim is still working on the drive system, which now is not so much "go-to" as "go-near". With the schiefspiegler's tiny field of view, this makes a big finder scope a necessary accessory. (Photo by Gary Garzone)

For more on the schiefspiegler design, here's a link to a web page of another amateur astronomer who designed and built his own tetra-mirror Brunn-schiefspiegler telescope. Here is a link to a page with instructions on how to build a simple, dual-mirror schiefspiegler telescope.