Laser collimations tools are excellent for achieving the finest optical alignment of your telescope. Unfortunately most don't come with instructions so we provide this following guide to help you.

Firstly, most lower-priced laser collimators themselves must be checked for correct collimation before use. Others like the self-centring HoTech models are preset at the factory for perfect collimation. This is because the are usually constructed as a metal housing with a red laser head fitted inside which is supported by three grub screws and during shipment from the manufacturer, subtle bumping and knocking may throw them out of whack. But, they can be adjusted just like the way you align a finderscope. See a video demonstration of the HoTech collimation tool here.

If you have a V-Block or V-shaped mini wine rack (like I use) you simply lay the collimator horizontally along it. Turn on the laser and direct the red dot beam to a point on a wall say 4 or 5 meters away. You can sticky tape a piece of paper at this spot and draw a circle around the projected laser dot. If you wish to have it super accurate then the further away the wall is, the larger will be the noted circular pattern or deviation from absolute centred.

Turn the laser collimator through 360 degrees. If it is well collimated you should see that the dot stays fairly well
within the tiny drawn circle or does not deviate from the dot reference mark on the paper. If not you need to adjust the collimation of the laser head. In our Optex laser collimator you will notice it has three Allen key grub screws that can be adjusted to pivot the internal laser head to the correct central position.
Just make small adjustments on each axis (one at a time) to see if the projected dot at your reference point deviates more or less. In other words, as you turn the laser collimator on its axis, if the laser dot produces are larger circular pattern then you are adjusting the wrong way and should back of the last adjustment. If the laser dot traces out a smaller circular pattern as you turn the collimator then you are heading in the right direction.

Once no deviating circular motion occurs when turning the collimation tool on its horizontal axis then it can now be used at the telescope.

Note also too,

AT THE TELESCOPE

First of all do a visual check to ensure a roughly collimation instrument using your eye as you already do. Check out our general guide to collimating your telescope here first before using your laser collimation tool.

After inserting in the focuser red laser, check secondary mirror alignment by looking down main tube to see if the red dot is in the centre of the black centre primary mirror marker. If not simply adjust the three tilt screws on the secondary mirror until the red dot falls on the primary mirror marker.

NOTE: If there is any slack in your telescopes focuser then this will alter accuracy of the collimation result. Be sure the laser is set into the focuser both flat and firmly tightened into place.

To adjust the main mirror turn the collimation tool around so the angled Cheshire is facing towards the back of the telescope. From here you can see the red dot on the Cheshire. The idea is that the beam must fall back in on itself. If it's out of alignment then you'll see the red dot on the metal Cheshire surface. By making adjustments to the primary mirror thumb screws you will see which direction the red dot is moving on the cheshire face. Adjust until the beam falls inside the laser collimator central hole.

Check at the front of the scope again and make sure red dot is still on centre mirror marker. If so, then you have a well collimated instrument.

Other Issues your Laser Collimator can Reveal

Aside from revealing how far out of collimation your telescope may be, a good laser collimation tool can reveal other defects in the optical train you sometimes don't expect. Things such as mirror flop, wobbly focuser or focuser assembly not seated flat to the optical tube. To check for mirror flop or sloppy focuser, (in the case of a Newtonian for example) after an initial collimation adjustment, move the telescope around on different angles looking from the rear of the instrument at the cheshire. If you notice that the red dot moves out from the central hole from where you had originally aligned to then it's likely the mirror is shifting in its mounting cell. The other possibly cause may be that shifting weight distribution at the focuser is revealing slop in the focuser shaft or fixtures. First re-check that the laser collimator is firmly fitted and tightened in the focuser. If so, lightly press against the rear mirror at various points while looking up at the laser collimator cheshire. If the red dot shifts then you know you have a little mirror flop occurring that will need adjustment for firm seating.

If the mirror seems ok, try applying a little pressure to the focuser drawtube - If any shift occurs then it should be tightened, padded out or simply replaced whatever the case my call for.