Laser Collimator
  Pictures Pictures

A laser collimator seemed like a really easy way to align my Dobsonian (Newtonian reflector) telescope, but the cost of commercial units was out of my budget.  What you see below is the design I came up with.  Total cost was about $20.00 with the laser pointer being about $17.00 of the total.

Ideally the collimator would be made from 1.25" od tube. Mine is made from 1.25" id tube, I just replace the focusers draw tube with the collimator when I use it.  The tube has a  .75" tall window cut into it for the viewing screen.  The viewing screen is made from a plastic milk carton.  The screen is a 1.25" disk with a .25" hole punched in the center.  It is glued into the main tube below the window.

There are eight screws which hold the laser pointer centered in the tube.  The eight screws are installed in Rivnuts.  Rivnuts, also called Nutserts, and other brand names which I don't know, are a combination of a pop rivet and a nut.  You drill a hole the size of the Rivnut, insert the Rivnut in the hole, and expand the Rivnut with a special tool.  Its a great way to put threads in thin material.  Harbor Freight and Tools  has a kit including the tool and Rivnuts for about $15.00.  The ninth screw is located over the laser pointers power switch.  I just tighten this screw to turn on the collimator, and loosen it to turn it off.

The black ring is a rubber O-ring to prevent me from inserting it to far into the focuser.

Aligning the Collimator

  1. Lay the collimator in two v-blocks.
  2. Look at the spot on a wall or some other surface about 10 feet away.
  3. Rotate the collimator.
  4. Adjust the eight screws until the spot remains stationary while the collimator is rotated.


  1. Insert the collimator in the focuser.
  2. Turn on the collimator.
  3. If you want to remove the diagonal, adjust the focuser so the laser spot hits the tube exactly opposite the focuser.
  4. Adjust the diagonal so the spot hits the center of the diagonal.
  5. Adjust the diagonal so the spot hits the center of the primary mirror, which should be marked.
  6. Adjust the primary mirror.  Initially the spot may be completely missing the diagonal.  Be careful the laser doesn't hit your eyes if you look in the tube to find the spot.  Work in this order: a - put the spot on the diagonal, b - put the spot back into the focuser draw tube, c- find the spot on the viewing screen in the focuser, when you are done the spot should disappear into the 1/4" hole in the center of the viewing screen.


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