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How-to Collimate a Laser Collimator
The best images come from the best optics, and the most effective way of improving ones optics is to get them aligned properly. The most significant advance in recent years in collimation devices is the Laser collimator. Not only is it more precise, it is simpler to move a laser dot than it is to align double images of cross hairs and dots seen in a Cheshire eyepiece. It can also be done in the dark! Furthermore, through the use of a 45 degree window, such as those in the EZCollimators (available from EZTelescope.com), one person can collimate the primary mirror from the back of the telescope without getting up and down to look through the top of the scope to see what that last adjustment did to the alignment.
That sounds like a pretty strong case for getting a laser collimator, right? But if the collimator beam is not perfectly on axis (and they do go out of adjustment just like telescope mirrors) you will be constantly mis-aligning your optics, rather than having them achieve their optimal performance. To ensure that you are not doing more harm than good, you should periodically check the alignment of your collimator. To do this, you need a jig to hold the collimator while you rotate it to check that the spot stays in one place. That is what this article is about.
All you need to test your collimator is a simple cradle. To make one, you need: a short piece of 1" x 6" pine, four #8 1.5" long deck screws, and some basic hand tools, such as a try square, "C"-clamp, hand saw, drill, screwdriver, and wood file to smooth the rough edges.
Layout of cuts andassembly locations
Layout and Cutting
First, lay out all your cuts in pencil (see left photo). Draw a line 3" from one end of the board. Then bisect this end down the middle of the board to form the two end supports. The remainder of the board will be the base of the cradle. Finally, lay out the notches on either side of the board that will hold the collimator. You want to support the collimator on its smoothest surface near either end. Mark a line in from each side of the board equal to the radius on each end of the collimator. Then draw a 45 degree line from the center of this line in either direction toward the edge of the board. This will ensure that the collimator contacts the two sides of the groove deep enough that it will not roll out while you are turning it.
It is easiest to make the groove cuts first, while you can hold onto the longer base portion of the board. Similarly, make the center cut down the end of the board before cutting off the end supports. Then position and mark where the end supports will go on the base plate. Mark a drill hole 3/4" in from each side of either support.
Drilling and Assembly
Now drill the four 1/8" clearance holes in the base plate. It also helps to drill out the angle for the head of the screw with a larger bit, although deck screws are designed to self-pilot and set themselves. On the bottom of the end supports, measure in 3/4" from one end, and drill a 3/32" pilot hole. All you need is one pilot hole per support to get you started; the deck screws can work their way into the support on the other hole without splitting the wood if centered properly. Insert one of the screws through the base plate and into the pilot hole. Screwing it snug, but not tight, swing the support into position and insert and tighten the second screw. Do this on the other end andyou are done!
Testing and Alignment
Completed test jig.
In order to test your collimator, clamp the base to a table with a C-clamp,
and aim it at a distant wall. Tape a blank paper on the wall and trace the image
of the red dot. Then rotate the collimator a quarter turn at a time and see
if the spot moves in a small circle. If it stays in one place, your collimator
is in perfect alignment.
If the spot moves, trace it at each quarter turn. Then mark an alignment target in the center of the four dots. Using the adjustment screwson the collimator, move the red dot to this target. Test and re-align if necessary until the dot stays put.
That's it! Now you can collimate your telescope with the confidence of knowing your collimator is working properly, and the results will be the best images your telescope can produce.