Richard Schwartz, in his patent 5,877,905 advocates the use of a six point support that has collimation bolts at a right angle. Considering how popular the alt-azimuth telescope is with amateurs, and considering how it is often easier for us to think in terms of right angles when collimating the main mirror...this approach has a great deal of appeal. Especially when you consider that an alt-az telescope does not rotate the mirror cell, so that the right angle collimation bolts can always remain as 'up/down' and 'left/right.' Here is one way to arrange a six point support with right-angle collimation bolts.

First we start with six support points on the back of the mirror. They have to be arranged in a ring of five with a central support, for a total of six.

Next, three beams (green) will support two points at each end of the beam. At the middle of the beams...

...will be three collimation bolts (red).

Here is the right angle (between collimation bolts) that I mentioned previously. Actually it's about 91.5 degrees, but that's much better than the 60 degree spacing you often find in mirror cell collimation bolt arrangements. The 1.5 degree deviation from a true right angle means that as you make an adjustment on one collimation bolt, your motion is not purely in only the vertical or only the horizontal direction. You end up having about 1/40th of your motion in one axis 'spill over' to the other axis. However, most of us, when making small/final collimation adjustments, would have a difficult time noticing that our final adjustment in one axis has 1/40th the motion in the other axis.

But how do you get a horizontal or vertical collimation motion out of this cell? Simple. When you build it, rotate it to an orientation such as this, and use only the upper and far right collimation bolts. Now your collimation motion will be almost purely horizontal and vertical. Enjoy!

Want to look up Richard's patent? Go here, and type 5,877,905 in the search box (make sure you include the comma's too).

All feedback is encouraged!

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Last update: 31 Dec 2002