Collimate Your Laser Collimator

As an amateur astronomer, you'll periodically hear people talk about how inaccurate your typical laser collimator, as I've done in this post. The truth is, the typical laser collimator that ships with your telescope is likely off by quite a bit, and any collimation you do with it will only end in a poorly collimated telescope. This is fixable, however, and can be quite simple to fix. Below, I'll show you the easy way to do this without any fancy equipment.

1. Insert the laser collimator into the focuser, as you typically would to collimate the telescope. Next, adjust the secondary mirror so that the laser completely misses the secondary mirror on the return trip and exits the objective. The telescope is now, in effect, a jig to hold the laser in a manner that it can be rotated without changing its position.
   
   
   
   When you do this, be very careful not to look into the laser beam. Always be mindful of where the laser beam is so you can avoid it.


2. Put a piece of paper at the end of a hallway and position the telescope so that the laser beam is on the paper. Mark the position on the paper, then rotate the laser 90 degrees and make another mark. Repeat this two more times and you will have a pattern like the one shown below. Now you have a square that shows you how far off your laser is. If the laser doesn't appear to move, then you're one of the lucky ones to get a pre-collimated laser.
   
   


3. Now use the adjustment screws to move the laser dot into the center of this square. On my Zhumell laser collimator, the screws are actually allen screws, so you'll need the appropriate allen key. The adjustment screws can typically be found on the main body of the collimator inside three holes. On some laser collimators, the adjustment screws may be hidden under the label.
   
   


4. Now just repeat this process until you've got the smallest square that the slop in your focuser allows. You'll never be able to get it perfect, but you can see in the following picture that you can get this square much smaller than when you started.
   
   

Now you can actually use your laser collimator to collimate your telescope! Keep in mind, however, that laser collimators can only be used to collimate the secondary mirror. The return beam is not guaranteed to be 100% accurate so still can't rely on the laser to collimate the primary mirror. For this, you still need to use a cheshire/sight-tube combo, but the laser can now make your collimation process much quicker!

Clear skies!