Beginners take on Collimation

[Ryan101 (Ryan)]

I recently sold my beloved Marshall stack guitar amp. It was the only way I was going to afford my Saxon 12" Dobsonian. And at 40 I've kind of given up on being a rock star.

I read heaps on collimation before committing to buying a reflector and was a bit nervous about the whole thing. There's so much info on the best way to collimate, and everyone's way is the best way. 'Do this and don't do that, but don't do that and do it this way.

So to make it easier I bought a $80 laser collimator.

It took about an hour to collimate the collimator. I got the telescope all set up, great. Back inside after my first night observing I thought it best to check the alignment of the mirrors and guess what, it was miles out. I realised I didn't have the target on the collimator facing the primary mirror so gave the laser a spin and guess what, it was pointing at a completely different spot. What to do?

I made myself a collimation cap to see if things looked different. It was obvious straight away that everything was miles out.
It took me about an hour to get everything lined up with the cap, mainly because it is all new to me but I got there.

So from a beginner to other potential beginners, don't let collimation worry you and don't fall for the cheap laser collimator. (maybe a Gary Glitter is a different story). A simple collimation cap will do fine to start off with. After I got it all aligned with the cap the first time I immediately put everything out of whack and collimate it again. Then I did this again. After that it only takes about 5 mins.

Everyone's way is the right way and everyone else's way is wrong. Practice with what you learn on and this will become your right way.

Cheers
Ryan.

[glend (Glen)]

You should have kept the Marshall. Music is not all about being a rock star and most musicians are not, you should be playing because you enjoy it, and believe me it keeps your brain Sharp in old age. I am over 70 and still playing everyday, even scales, haha. My grand kids love the video covers I send to them playing the guitar. Even Disney songs.

[Ryan101 (Ryan)]

Haha, I haven't played electric or steel string for about 15yrs I reckon. All classically for me now!

[sunslayr (David)]

The real advantage to a (collimated) laser collimator is being able to adjust the primary without having to run back and forth from the back of your ota to the eye piece. Putting it in a Barlow gives it a little more precision too. Maybe you should try adjusting it yourself with a couple of angle brackets, I had to do that with mine.

[mental4astro (Alexander)]

Ryan,

When it comes to collimation, the hardest part is just the term "collimation". It only means "aligning the optics".

Too much is made of this process being difficult, and this scares off many people from using Newts. People are not familiar with the term, read about things such as Cheshire eyepiece, auto collimator and then LASERS, and OMG!!! FREAK OUT!!

Collimating tips
There is plenty of info on collimating Newts, and Astro Baby's site is one of the best for newcomers to follow.

There are two things you need to be aware of when it comes to sorting out the mirrors of a Newt:

1, Get the secondary mirror right FIRST!

The secondary is the ugly cousin of the primary and is not recognized by new comers as being just as critical as the primary in the optical train. Not get the secondary sorted first & it doesn't matter what you do with the primary, the alignment of the optics won't work out.

Mess around with the primary first, and you are asking for a world of pain and frustration with the process

2, A laser alone will not do it all!

A laser WILL NOT fix the secondary. A laser is only a tool to help tweak the primary only after the secondary has been sorted out. A laser will not tell you if the secondary is square with the focuser, nor if it is centered with the focuser draw tube, nor if it is sufficiently aligned with the primary. This is the purpose of the Cheshire Eyepiece and the Auto Collimator (collimation cap).

It is possible to "collimate" a Newt with only a laser, but it will be a false collimation, and over time the secondary will be more and more misaligned and the final image will just get worse and worse. This is entirely because the secondary has not been proplerly sorted because a laser cannot determine the unique job/requirements/position of the secondary.

Actually, a laser is not necessary at all! It is only a convenient tool to make the tweaking easier. A Cheshire eyepiece is all that is needed, and star testing to tweak the final part of the primary, which in reality even when using a laser, a star test should be the final verification test that everything is right... but I too am a creature of comfort and I do use a laser, but I also use both a Cheshire eyepiiece and collimation cap to sort out the secondary first.

The terms "primary" & "secondary" are often confused with meaning an order of significance. Truth is that when it comes to aligning Newts, it is the secondary that comes first, not the other way around. And I too made this mistake too when I started out with Newts. I did not understand the role of the secondary in the optical train and I also thought a laser would do it all. I hope this post will help out you and everyone else new to collimating to avoid some of the traps that are not immediately obvious and that astro retailers just cannot know your experience in collimation when you buy a laser from them.

Alex.

[Ryan101 (Ryan)]

I'm happy with how I got the laser collimate, it just seems to have to much play in the focuser. Any advise on how to hold the laser straight in the focuser would be greatly appreciated.

[Ryan101 (Ryan)]

Thanks for the advise Alex.

I think I'll just ditch the laser all together. As a bigginer a laser is sold as being the answer to all the collimation worries. I think it causes more problems than what it's worth.

Cheers

[mental4astro (Alexander)]

NO, DON'T DITCH THE LASER!!!

They are not more trouble than they are worth! Not by a long shot. They just need to be used in the right way!

They are a very convenient tool in the collimation process, as David mentioned.

Knowing this, and that a Cheshire will do it all, if you forget your laser, or found that its batteries are flat, you won't be crippled. And even if you forget your Cheshire, there are other "get out of jail" in-the-field tricks that will help at a pinch

Alex.

[AdamJL]

Originally Posted by mental4astro

and this scares off many people from using Newts.

This is me. Hence I bought a refractor :S
I know I might need to fiddle with a refractor but the idea of doing that with a Newt just didn't seem very enticing to a newbie. There's enough to learn without adding something else on.

Maybe in future I'll look into a newt.

[mental4astro (Alexander)]

Originally Posted by AdamJL

This is me. Hence I bought a refractor :S

And this is not a bad decision if you are unsure

One thing that helps to keep in mind with the tweaking of Newts is that by giving the Newt some TLC, you will be getting the very best out of the scope. You don't buy a scope to get a mediocre image/view, so the minutes it takes is entirely to your benefit.

But why does a Newt need such constant tweaking? (and the tweaking is only small touches)

The main reason is how Newts are built - essentially on a bunch of springs. This is to help keep the glass mirrors sitting passive in their cells. Over tightening the clips that hold the primary mirror in place, and this takes a surprisingly little amount of force, and it is enough to distort the delicate, finely ground reflective face! You might think that holding a mirror hard and fast in place is a good idea - no it isn't! If t he glass if warmed, it will expand, and if it is held hard and fast in place, it will be just like over tightening the retention clips, and the precious figures of the mirror is distorted - remember, we are talking about wavelengths of light. So the more the scope is moved about, set up & taken down, taken to a dark site, etc, these springs and screws will jostle and reset themselves as they seek to relieve the strain induced into them.

This is the trade off in getting larger aperture.

Even the giant scopes used in professional observatories need constant tweaking! These machines, despite the fine quality of the optics and machine, these are also susceptible to moving, and collimation needs tweaking!

And another thing to note about these professional scopes is while most do use lasers in the collimation process, the final verification of the collimation is ALWAYS done by star testing - the very same thing we do!

Alex.

[Ryan101 (Ryan)]

Don't get me wrong, I love the idea of a laser. If I could only get the thing to sit snug and straight in the focuser. I guess it's something all beginners have to figure out. That and making adjustments in the dark off a star test.

[mental4astro (Alexander)]

What laser are you using, Ryan?

[Ryan101 (Ryan)]

It's supposed to be a saxon branded one but it is just one of those next or new generation ones. Adjustable brightness and all. It looks like the ones on ebay for about $20-$30.

[mental4astro (Alexander)]

I am familiar with those laser collimators.

Are you using it as a 2" unit or 1.25"?

How are you finding it not fitting snug?

I need to ask these Q's so we can give the best solution.

If it is a little loose, a wrap or two of sticky tape often does the trick. Another is to push it onto the focuser drawtube when you tighten the set screw. This way you assure that it is sitting square on the drawtube.

[Startrek (Martin)]

Ryan
Alex gives excellent advice and in my opinion is the “Guru of Newts”
I have exclusively observed and imaged with newts 6” , 8” , 10” and 12” over the past 4 years
My imaging newts are removed from their mounts and packed away in my garage every 2 weeks or so. I rarely have to tweak alignment as they hold Collimation really well , I use both GSO and Skywatcher newts so budget low end scopes
I fitted new primary mirror springs ( Better Spring - plug ) to my 6” f6 newt and it mage Collimation so much easier , the original GSO springs were poor quality and compressed to easily
I use an Orion Collimating eye piece ( Cheshire ) to align the secondary first and and Primary second and an Orion Lasermate Deluxe Mk11 Collimator for a final tweak
Good luck and enjoy this amazing hobby
Martin
Newt Man through and through

[Ryan101 (Ryan)]

Alex, I must thank you again for all of your help.

I'm using it as a 1.25" and it just seems to have a little play when I move it from side to side. I can also see it move over slightly when I tighten the screws a little.

That sticky tape trick seems so obvious that I don't know why I didn't think of it. I'll give that a go.

Cheers.