collamateing of heritage 130p truss

[mr saddo]

Hi there, just bought a lazer collimator, i had aright job last night trying to do the scope i have a few questions on the matter for a heritage 130p truss dob, oh yeah i have collimated the lazer it was way out!!

1. do you have the scope level , or pointing up at say 45 degrees when collimating? has you would use the scope when stargazing.

2, focuser in or out? this is a helix type screw in and there is a lot of slop in it when halfway out. which effects the red dot n lazer mirror.

3. the red dot on the lazer is on the edge of the dough-nut on main mirror, yet it is central in the window on the lazer after i have moved main mirror screws is this right?

4. ive seen a vid on you tube they say to move your front mirror so the red dot is in the middle of the dough nut on the main mirror tried that then the 3 mirror clips are way out. i could not get the dot in middle, but on the edge of dough nut was best i could do. yours paul.

[Damo636]

Hi Paul. The first thing you need to do is center your secondary mirror with a collimation cap or cheshire/sighttube. A 35mm film canister with a small hole in the top will do the job if you don't have either. When you are happy that the secondary is centered then insert the laser. Adjust the secondary mirror until the beam falls inside the doughnut on the primary mirror. Then adjust the primary until the beam falls back on itself and centered in the laser collimator. As you have some slop in your focuser i would use the laser with the focuser racked fully in to minimise it best you can. HTH

[umadog]

Answers:

1. It doesn't really matter but you might as well do 45 degrees. I give the tube a hard wiggle before hand to help stuff "settle in."

2. Set the focuser to roughly the position it should be when you're viewing. Put the laser into the focuser and rack in and out. How much does the beam move?

3. No. You need to do things in the correct order as described by the previous poster. Adjust the secondary until the beam is in the middle of the primary. Then adjust the return beam. Iterate back and forth until both are correct. The return beam is more important. Barlow it if you can for the return beam. That way it won't matter if the laser is out of alignment.

4. If the mirror clips are "way out" then you need to centre the secondary in the focuser using a sight-tube (as in the cross-hair bit found on a Cheshire/sight-tube combination tool). Remember that if your secondary is a touch on the small side then you will *not* be able to see all the clips at the same time. The purpose of seeing the clips is just as an indicator that the primary is centered in the secondary. If the primary is too big for the secondary than this won't be possible. In this case just make sure the secondary is round and centred in the focuser and the primary donut is centred in the cross-hairs (or you're hitting it with the laser).

Remember:

* first pass of laser to primary = sight-tube

* second pass of laser back to focuser = cheshire

Also, just so you know, laser is with an "s": for light amplification by Stimulated emission of radiation. The substance in the laser cavity is stimulated by light and itself emits light.

[mr saddo]

Hi there, thanks for that.