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View Full Version here: : Collimation conundrum


southerncross
31-01-2010, 03:37 AM
Gidday All
Well I finally received my new Hotech 2" crosshair laser collimator, took a while to arrive so I was quite excited to test it out, this is where things started to go downhill. :(

Prior to this I had only a few evenings to use my scope as cloud cover has been constant since it arrived ( 8" skywatcher Dob), I had one good night of gaps in the cloud and got a hold of Mars but it was quite bright with no detail, I did tho do a "star test" and while I had very crisp concentric circles I did noticed some crimping around the primary mounts.

Anyways I got my laser collimator, decided to check it out, removed the gadgetry from my focuser sleeve only to find that my collimator would not fit the sleeve without the 2" thumb screw adaptor.

Q.1 Does this not defeat the purpose of the new beaut Hotech SCA system?

So after this I turned on my laser collimator to find that my scope was pretty darn well aligned to within a bees dick of were it should be, I could not let that rest though after reading Vic Menard's Newt Collimation Book from front to back a number of times in the weeks it took my Laser Collimator to arrive, I just had to Tinker with things.
It all seemed straight forward Tweak it here turn a screw there Viola all good, all Smicko, Simple as.....But then as I moved my scope from horizontal to vertical and watching the viewfinder on the collimator I noticed it did not stay on the center spot as I moved it....MMMM

Oh well I thought... it must be me (MUST BE), Scopes good, Book's Good, Laser Collimator is Good, Ill just start from the beginning and do it all by the book, DUUNG DOONG.

Adjust the secondary to the centre spot, adjust the primary to the veiwfinder...Same result, still movement of the laser spot upon going to the vertical....MMMM. Bugger

At this stage I resorted to the book and decided to go the whole hog and go for THE NEW METHOD, Why not seemed simple enough.....
Until I try to centre my secondary mirror and find that my Optical tube is not completely round (out by 3mm), My spider vanes change the centre spot alignment by 2-3 mm when they are touched after tightening, (IE they warp one way or another when tightened) and My primary does not seem to be attached to anything other than the adjustment screws (IE it flops once I undo either of the adjustment screws and the other two are loosened).
Is it the Skywatcher Scope or Me, Ive loosened, tightened, wiggled , waggled, read yet again, Redone numerous times, measured, etc etc etc.

I'm really getting Crainally Intercoursed by all this and need some informed advice on what to do. PLUHEESE:question:

el_draco
31-01-2010, 12:12 PM
Never heard that one before.... I'm going to add itto my reports! :lol: :lol:
:lol:

astro_nutt
01-02-2010, 10:57 AM
Hi Jeff,
Here's a couple of things to try out.
1. Make sure the focuser and connecting sleeves, adaptors are firmly in place and the focuser itself has no play whilst focusing in and out.
2. The locking screws for the primary mirror only need to be finger tight, not too firm. Once that is done see if the primary mirror is able to move around by pushing it from behind. If so, check to see if the adjustment screws are threaded into the mirror cell, also, check the clips holding the mirror in it's cell. They should only tightened up enough to touch the mirror's edge.
3. Check the lock screw in the centre of the secondary mirror holder. Again it only needs to finger tight as are the collimation screws.
Good luck!

southerncross
03-02-2010, 01:17 AM
Thanks for the reply Astro_nutt, problem is solved now (I hope).