Collimation advice

[Neil H]

Hi I would like some advice on Collimation please . Ok to Try and keep short I have a laser Collimation tool which I test and was out so adjusted and is now spot on , when I collimator I take my time and get it 100% , now for what's happenings

I collimate the telescope so it's spot on later on I let it cool down outside of I check Collimation it's out a lot out 

So now i take telescope out to cool down and collimate once it's cooled down i get it 100% (pain in the dark it has a plate on the back tiny screws) if after 1 to 2 hours I recheck the Collimation it out by a lot again , is this normal ?

It's not just this telescope ( skywatcher 150/750 F5 ) my old ( powerseeker 114 ) did the same 

Do you just collimate your scope and just not check it till the next time you set up for the night viewing ?

Am I being or worried about Collimation ?

[joe aguiar]

There should be 6 screws or 3 sets of 2

3 screws tilt the mirror 3 lock it, are u locking them. Then is 2nd mirror aligned in focuser sight.

Once done it should hold for many months even more if it's just from inside to backyard 

If it's taken into car all the time to other sites then all those vibrations can be once a month.  But not every session 

Joejaguar 

[NGC 1502]

Tough to know what’s happening.....

One reason that your collimation doesn’t hold is if something is loose -

Although mirrors should never be held tightly, if they’re allowed too much slack the they can shift and alter the collimation.

For the primary mirror the clips just need very tiny clearance from the optical surface.  Check mirror cell to tube is secure.  Also check the spider vanes are not too slack, secondary holder is not loose.

Or - if you check collimation with your laser, then check later with the laser, is it slack where it fits the focuser ? Could be what’s causing the problem.

You could try collimation with a basic collimation cap, then fine tune with a star test, in other words - ditch the laser.....some regard laser collimators as an expensive way to stuff your telescope 😳

Hope you sort it, Ed.

Edited February 11, 2020 by NGC 1502
correction

[Neil H]

Hi guys everything is tight ( I know it's all in place I flocked it the other day )and I do up the locking screws I wonder if it's the rubber O rings it's a skywatcher 150/750 and there are tiny rubber O rings between the mirror back and casing which the locking screws go though , I saw on here some were , that a few guys took out the rubber O rings and replaced with tiny springs  when you do up the locking screws the Collimation moves but you can using the locking screws get it right,may be I should collimate and forget then I wouldn't know its out, image looks ok moon is really sharp and Venus seems to be a sharp point of light 

At a loss really 

[Neil H]

ED  and Joe would doing up locking screws to tight make the Collimation keep changing over the hour 

[Neil H]

Quick update I collimated it again this time the locking screws are just holding the mirror 

The locking screws go into the mirror mounting plate the tiny adjustment screws press on the mount so it's easy to over tighten the locking screws and pull on the mirror mount or have I got it wrong and the what I think are locking screws are not and are the adjustment screws and the little Allan screws are the locking screws as they press on the back of the mirror mount ? More investigations needed 

Edited February 12, 2020 by Neil H

[Neil H]

I have just got the manual on line and I Am using the wrong screws derr what a thickO I am, ok so this maybe my problem I will go and collimate it again lol 

Ok all collimated  see how it goes

I think what confused me when I stripped to flock it I found the rubber O rings was on the little grub screws which is wrong I put them back on the bigger screws were they are ment to go but I didn't put 2&2 together and work out these are adjustment screws it didn't click till I was thinking about the thread of changing the rubber rings into springs . Then the light went on 

Edited February 12, 2020 by Neil H
More info

[joe aguiar]

ok sound like u got it

joe

[Neil H]

Hi Joe I hope so , This is an amazing hobby love all the learning that's involved , as I am At the moment stuck in the back yard mostly I look at the moon ,Orion and Venus if I am quick before it goes behind next door house , I never get tired looking at Orion stars and nebulae 

And  big thanks to everyone on here helping me progress in this hobby 

[wookie1965]

I was told to screw in the adjustment screws in all the way then back them off 1. 5 times from there collimate as usual then gently use locking screws taking care to look if the mirror moves. 

If the primary is set right that will stay in place unless you bang the OTA

To collimate in the dark, 

Simple, get a laser collimator, ensure that it's collimated. Insert it into a Barlow and ensure that your focuser is wound in. If collimated you should see the outline of your primary centre circle ( marker) on the collimator screen. Minor adjustments with the primary adjusters will make this dead reflection centre. 

My 150p needed a tweak every time I took it out. 

[Neil H]

Yeah found that with mine too