Collimation - Whats the fuss all about?

[Digz]

Last week I took delivery of my Baader Laser Collimator and today set about collimating my scope.

Having read all the stories on collimation and how difficult it was supposed to be, I was ready for a fight on my hands. Well, lets just say I won hands down, a clean TKO in round 1.

The basic process:

I used an old Celestron SR4 eyepiece with the lenses removed as a collimation cap (the exit pupil size was perfect) to check the secondary mirror was centred and circular. (I also used a couple of tricks picked up from Astro Baby's site: Astro Babys Guide to Collimation - cheers AB )

The laser collimator was then popped into the my scope. I could see the laser dot was slightly to the right of the centrespot on my primary mirror. A slight tweak of my secodnary brought that spot on.

Now to tweak the primary mirror to ensure the return laser was centred.

Job done.

The scope wasnt a million miles out in the first place, but it will be interesting to see the difference now its spot on.

[LMC]

Me too!!!!

I thought I was going to have some kind of seizure the first time.

I was fully prepared to spend an hour or so getting it spot-on.

Using a laser collimator made it a 2 minute job.

Any decent one is highly recommended. I use a Glatter but there are loads out there.

For some reason there are whole books written about the subject.

I saw one today titled "A new approach to collimation" or some-such. "A new approach..."?

Go slow and just get the dot in the centre of the ring.

You'll be fine.

[Jason D]

There are those lucky ones who receive well-collimated scopes from the manufacturers -- or need minor tweaks.

There are those who are not as lucky. Their scopes would need major effort to collimate.

There are those who think they collimated their scopes when they did not.

There are those who have good collimated scopes but demand perfection. Going that last mile of perfection is much tougher than the first 99 miles.

It is hard to generalize especially when there are many threads seeking collimation assistance.

But it really comes down to self-satisfaction. As long as the scope owner is happy with his/her collimation, that what counts.

[Digz]

There are many threads seeking collimation assistance and I guess I was lucky that mine wasn't that far out. Having said that, I followed the procedure for collimation, even if nothing was adjusted i.e. worked through the steps.

It is an easy process to do and thats the point I was making. Having read all the threads I was anticipating a tough time and the actual process is easy to go through.

[Chris H]

Have you checked whether you laser collimator is collimated? Despite what Baader say my laser was miles out.

[Digz]

I must admit I havent, but I cant see how I could adjust it if was out? Ive got the MkIII collimator and there is no visible sign of adjustment.

[pook]

Oh.. it's easy all right. I did it in 5 minutes when I bought my new scope. The issue was it wasn't accurate. My laser itself wasn't collimated.

I've given up on lasers. Get it close with a cheshire or collimating cap, and then do a star test. You can't argue with a star test.

[perfrej]

I agree totally. My collimator was way off and I got it swapped for another one. That one was a bit off too, so I collimated it. I had to tear out two rubber seals to get at the adjustment screws, but once I got to them I had the thing straight in about five minutes.

Try rotating your collimator in the focuser slowly and with firm pressure into the opening. Chances are close to 100 percent it is a bit off. I had about a centimeter circle on the good one.

/p

[John]

I agree with the other posters here, until you star test, don't believe the scope is collimated !.

The Baader laser collimators are very difficult to collimate if they are not spot on because of their non-symmetrical body shape.

[Digz]

Well I checked my Baader, using my puck as a base and it is indeed perfectly centred. Checked several times continuously rotating and the laser beam didn't stray one bit.

[John]

Well I checked my Baader, using my puck as a base and it is indeed perfectly centred. Checked several times continuously rotating and the laser beam didn't stray one bit.

Thats great - they are good collimators when centered properly, just pigs when that's not the case.

It's still worth checking things out with a star test when you get a chance - it's the ultimate test

[Digz]

It's still worth checking things out with a star test when you get a chance - it's the ultimate test

Definitely

Just so Im clear the star test is viewing a defocussed star (both focussed to far in and too far out?) to ensure a symmetrical pattern?

Not a very scientific description but thats my understanding

[Parus major]

Have you checked whether you laser collimator is collimated? Despite what Baader say my laser was miles out.

I have a Baader one as well and when I checked it it could draw a 4cm circle at 4m which equates to being way off!

AE cheshire and I'm all set.

[John]

I have a Baader one as well and when I checked it it could draw a 4cm circle at 4m which equates to being way off!

AE cheshire and I'm all set.

That is way off !

My cheapo revelation is now (after much mucking about ) adjusted so that the spot stays more or less stationary at around 8m.

Even with that I use barlowed laser collimation plus star testing for more precise alignment.

[stolenfeather]

When my time comes, I can pnly hope it goes as well as you!

Isabelle

[pook]

Definitely

Just so Im clear the star test is viewing a defocussed star (both focussed to far in and too far out?) to ensure a symmetrical pattern?

Not a very scientific description but thats my understanding

Yes. You need a lot of mag though, so around 150-200x and a bright star.. Aldeberan should be high enough to use round about now. The scope needs to be cool and seeing needs to be good.

[Orion_the_Hunter]

When my scope arrived, it was way out. Collimation was a nightmare and I had to straighen out the secondary holder.

Now I check it before every use & it's easy!

[Digz]

Cheers Pook.

Just done a star test and it looks pretty spot to me

[Peter Drew]

When star test collimating don't go too far in or out of focus, what can look like a nice symmetrical image way out of focus can often degenerate to off centre very near the focus. If you get that annoying appearance of perfect collimation one side of focus but out on the other side it's time to check your focuser alignment. .

[Jannis]

I have still not collimated my explorer 200p, it seemed OK when i bought it, and haven't bought any lazer for it. Would you easily see it in teh pics if collimation is needed?

[Digz]

My understanding is that stars become oval shaped with poor collimation.

[John]

My understanding is that stars become oval shaped with poor collimation.

If the collimation is out you loose resolution and contrast, especially on planets. So unless you have a well collimated scope to compare it too, you may not notice the issue.

The collimation "sweet spot" gets smaller as the scope gets faster - F/8 newtonians can tolerate a little mis-collimation but F/5's need it to be as accurate as possible.

[Digz]

Ah, cheers for clearing that up John

[Jannis]

Ok, so i guess i should just get myself a little money saved up and buy a lazer then? But, hmm, after reading all this about how unacurate the lazers themselvs are collimated, i'm unsure if i can trust the lazer anyway... ;

[Digz]

Lasers are good as long as they are colimated themselves. This is easily done.

One thing which is also worth considering is the thread in the Tutorial section on using a Barlowed Laser:

http://stargazerslounge.com/primers-tutorials/84752-barlowed-laser-collimation-method.html

A very good check method which doesn't rely on a perfectly collimated laser.