Squaring up that cheap laser collimator
(as featured in Star Ware, 4th Ed)Ever wonder if that inexpensive laser collimator is doing more harm than good? Know your laser collimator isn't collimated and want to adjust it to make it so? As lazy as I am? Read on. It'll take you longer to read this short page than it will to build the Lazy Laser Collimator Collimator (LLCC) and the electricity used by your computer while you read it will likely cost more than the LLCC itself.
When I bought my "Deluxe" laser collimator, I knew it was out of whack. Not that the vendor had done anything wrong mind you, but that the cap that you had to remove to get to the battery was stiff enough that I thought it was held in place by three small allen screws. Nope -- those were the adjustment screws. Screwing those screws had me screwed, or so I thought.
The whole deal with a laser collimator is to send out a beam of light that is perfectly parallel to the axis of your focuser. That way, it'll hit the secondary and then the primary where you can adjust the secondary to have the beam hit the center of the secondary. The beam then goes back up, hits the secondary and then back to the origin where a target lets you know if you're not aligned. All this is based on the premise that your beam starts off in a straight line and not at an angle. Mine was clearly at an angle.
OK, so I've got those 3 screws to adjust the angle of the beam (they push on a small laser pointer embedded in the device. But, how to know when it's straight? Well, if you rotate the device around while holding it still, a beam that's parallel to the device will make a dot. A beam that's off at an angle will make a circle.
I tried doing this using my focuser but to no real avail. The focuser moved a smidge and my max distance was ~40 inches (the f/l of the available scope). I'd read a site on the web about holding the laser collimator in a simple device that consisted of a horizontal base plate and two vertical pieces with V-shaped notches cut out. Sounds like a fine plan. But, I'm lazy. That'd mean cutting out the V-shaped notches, making them close to straight, and gluing the pieces together. Grand total might actually be 15 minutes to build the thing.
Can you tell just how lazy I can be? Rather, how long I'll spend thinking of a way to save a few minutes?
Enter the solution below. 1 block of scrap wood, 4 nails for the basic version and 5 for the "ultra-mega deluxe" version
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I told you it was easy, right? Anybody can do this. I used 2 1/2" common nails but anything will do (just try to not use ones with ridges that'll mar your collimator). Put 2 in a V at one end, put your collimator roughly in place to determine where the other V goes and you're done. What angle? Doesn't matter. Do they need to be symmetrical? No. Do they need to make a line parallel to the wood? No. Do I need to measure a darn thing? No. Are there to-scale drawings available for download? Sure. Send me $10 and I'll make some for you...
Now, for the piece de resistance -- The Ultra Mega Deluxe upgrade (an additional $10 for scale drawings with it). Put your collimator between the two V's and find where you can rotate it without having your on/off button or the adjustment screws hit by the nails. Then, place another nail vertically at the front, offset by exactly 11/32" from the laser beam. If your measurement is off by even 1/2", it's possible it won't work. With this, you can now rotate the laser collimator without it moving fore-aft and falling off one of the V's (send another $10 and I'll give you detailed instructions on how to achieve this accuracy in placement).
The not-as-fun part
OK, you've now built the LLCC, it's time to use it. Drop the laser collimator between the V's and place it on a solid surface aiming at a wall 10+ feet away. Rotate the laser collimator and see if you make a circle or if it stays a dot. If it makes a circle, adjust your collimation screws (loosen first, then tighten) and see if the problem is better. It may help to mark the wall where the center of the circle is (and clamp the LLCC in place) to let you know if you fixed one angle and made another. Anyway, it took me ~6 iterations before I got mine down (it helped to unscrew the back of mine to have easy access to the laser pointer inside to nudge it a bit here and there). Now, I'm nicely lined up.