Thursday, June 15, 2023

I Have Blogged This Before

I am hoping it sticks this time.  Collimating a Newtonian reflector is the difference between fuzzy round images of Jupiter and Jupiter with cloud bands; Saturn as an oblong disk and Saturn with distinct rings and (potentially) Cassini's Division in the rings.


1. Aim the telescope into a relatively dark room or area if you are foolishly trying to do it in daylight (like right now). 

2. Put laser collimator in focuser.  Turn on.  

3. Look for red dot on wall in dark area.  If you do not see it, the optical train is either already pretty close or the laser beam is hitting the diagonal so far from square that it is not hitting the primary mirror, or the primary mirror is not square to the tube 

4.  Look in the tube to see if you can see the beam.  If you cannot get the beam (briefly) in your eye, is it hitting the primary and then reflecting on to the inside of the tube?  If so, your diagonal mirror is either far from square to mirror and focuser or the primary mirror is not square to the tube.  Fix each.  

5. The beam should be hitting the primary mirror.  Adjust the diagonal holder screws until the beam hits the little dot or if you have a new or recently recoated mirror in the center of the little white circle.

6. Now go to the primary end of the scope.  Adjust the collimation screws on the mirror cell until the red dot on the dark wall disappears.  This means it is hitting the diagonal.

7. If this is a long focal ratio telescope, you may need to go from primary mirror end and back several times, adjusting the collimation screws until the beam is hitting centrally enough on the collimator to appear on the output display (or whatever you call the place where the beam shows up in the collimator).

8. You should see some red glow somewhere on that screen.  Adjust collimation screws on primary mirror until you get a red dot.

9. Adjust collimation screws until beam hits the center hole of the screen and turns into a large indistinct blob.

10. I have not seen these locking screws on any recent mirror cell.  If you have them, screw them down until they touch the cell inner body. This should reduce need for frequent future collimation.

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