Collimation help!

[Patrick1948]

Just a quickie on collimation...I have a 10" Dob and before the clouds clear I want to collimate it (sounds quite rude doesn't it??) just let me run this procedure past you expert people...I bought a laser collimator and at the risk of appearing as thick as two short planks, the instructions didn't appear quite clear to me.....so....(I'm sitting at the rear of the scope, which is horizontal, looking along the scope to the front)... I inserted the collimator into the eyepiece hole and with the window of the collimator facing the primary mirror end of the scope, turned it on....the red dot was way off the centre of the bulls eye.....I then loosened the locking screws and adjusted the mirror by adjusting the three adjusting screws until the red dot was bang in the centre of the target.....then tightened up the locking screws.

Is that it???? I must admit I was quaking in my boots at the thought of messing about with such an important part of the scope and ...well... it all seemed too easy. Does it sound as though I did it right?

[gfletcher]

Hi Patrick

The procedure is:

After inserting the laser collimator in the focuser tube and turning on the laser, if the red laser dot is not in the middle of the primary mirror you need to adjust the secondary mirror (by means of adjustment of the 3 screws/socket head grub screws) until you achieve the dot in the centre of the primary.

Once done you then look (from the primary mirror end of the scope) at the targer ring on the laser collimator.

If the red laser dot is not central on this target ring you need to adjust the screws on the primary mirror until this is achieved.

HTH

Graham

[glennbech]

.... I usually use the laser for only the first step, and a Cheshire for the final step. In my experience, the laser is way to sensitive when it can travel "back and forth". Even adjusting the laser collimator slightly in the EP holder can move the beam.

[Patrick1948]

Thanks Grahm, very well explained.....I did do it wrong!!! I'll fix it tomorrow in time for the clear skies that are forecast.