Collimation tools help for newbie

[offfoo182]

Hi all, 

I’m getting really confused with collimation. I’ve read a big post by Astro baby but wanted to clarify a few things.

I’ve got a 10” F4.8 Newtonian and ordered a Baader steeltrack focuser. 

My focuser will do 2” and 1.25”.

I have the Baader vip Barlow  which again will do both sizes.. I have a cheap nasty laser which has been causing me all sorts of problems and cannot be collimated.

For my speed of telescope would a 2” collimation cap and using my cheap laser in my Barlow cover all aspects of collimation?

Or do I need to spend big bucks and buy something like the OCAL electric Collimator?

Primary mirror alignment 
Secondary mirror alignment 
Making the secondary mirror look like a circle. 
Aligning the secondary mirror in the centre of the tube/mirror.

Are these all the steps (not in order) I need to cover and what equipment will cover what?

I’m new to the hobby so don’t assume I know anything 😂🙈

I only do visual at the moment but I’m making sure all my equipment can transition to astrophotography in the future to save buying twice. 
 

thanks all in advance!

Sean

[Astronomist]

I would highly recommend this Cheshire eyepiece - a good solid well made item, at a very reasonable price

https://www.firstlightoptics.com/other-collimation-tools/stellalyra-premium-cheshire-collimating-eyepiece.html

 

[Carbon Brush]

Hello Sean and welcome to the forum.

Collimation on newtonians is (in my opinion) much over-thought.
You can start with a low cost Cheshire - and for you a basic laser.

From my experience, your biggest issue is going to be the length of your arms.
A strange response? With that size of tube can you look down the eyepiece and reach the main mirror screws?

I use a laser on big newts quite simply so I can view the spot from a distance while working the main mirror screws.

It would be a good idea to check things out using the original focusser first.
Swapping focusser will add 'did I do it right' type of questions.

If the main mirror has not been centre spotted, that is the first job.

I assume the scope has a previous owner? Was anything said about collimation tools?

There is no rush with collimation and you can do it in warm and daylight conditions.
It is only later that you get to do a star test - which relies on good viewing.

A warning on scope construction. Until you know otherwise, it is not a good idea to assume the scope only needs collimation.
For example check the focus tube is aligned to the secondary.
This and other construction issues can send you round in circles.
Been there and got the T shirt on a NEW Orion Optics scope many years ago.

HTH, David.

[offfoo182]

Thanks!

I’ve done it with the old focuser and didn’t realise the laser could be out. Tested it by twisting and it’s no wonder my planets were just fuzzy balls with no definition.

it’s too long to reach hence the laser which I guess I can use with my Barlow.

what does the Cheshire do? Help line up the mirrors?

I have centre spotted it yesterday which should help.

I live ten minutes from Orion and they are going to fit the new focuser (requires cutting which is beyond me) am I safe to assume they will make sure the focus tube and secondary are aligned?

what tools do I need to check that? Will the Cheshire do that?

 

thanks again!

Edited December 10, 2022 by offfoo182
Mistake

[offfoo182]

36 minutes ago, Astronomist said:

I would highly recommend this Cheshire eyepiece - a good solid well made item, at a very reasonable price

https://www.firstlightoptics.com/other-collimation-tools/stellalyra-premium-cheshire-collimating-eyepiece.html

 

Thanks!

[Carbon Brush]

Ah. If Orion are fitting the focusser, you can get them to show you collimation when you collect.
I have always found a practical demonstration better than books or videos.

A Cheshire allows you to see the alignment (or errors).
On a small scope (or big scope with willing assistant) it can be all you need.

On a big newt that is new to me, I roughly follow....
Am I happy the focus unit is sited correctly? Over the secondary.
Does the laser (if used) shine on the same part of the secondary when the focus is racked in/out.
It may be necessary to adjust the focus tilt.
Is the secondary correctly placed in the tube centre? Check the spider lengths.

Now check the primary position and approximate alignment.
Place the tube horizontal and take a short walk.
Looking back at the scope, is the mirror central to the tube? It should be.
You are looking for concentric circles formed by tube and mirror.

Next, can you see yourself reflected? Probably not.
Some primary adjustment (using an assistant) will help align the scope machanical axis (tube) to the optical axis.
Yes I have seen scopes with main mirrors looking way off to one side!

At this point you are ready to look at collimation. Following whatever guide you find helpful.

Having got the big problems (if they are there) out of the way, you can be sure the scope is correctly assembled.
From one outing to the next you will find a glance down a Cheshire or a few seconds of laser will confirm alignment.
If collimation does change significantly, or often, you probably have a screw loose somewhere (no offence intended🤣).
Unless the tube gets a real hard whack, scopes hold collimation for a long time.

HTH, David.

 

[offfoo182]

2 hours ago, Carbon Brush said:

Ah. If Orion are fitting the focusser, you can get them to show you collimation when you collect.
I have always found a practical demonstration better than books or videos.

A Cheshire allows you to see the alignment (or errors).
On a small scope (or big scope with willing assistant) it can be all you need.

On a big newt that is new to me, I roughly follow....
Am I happy the focus unit is sited correctly? Over the secondary.
Does the laser (if used) shine on the same part of the secondary when the focus is racked in/out.
It may be necessary to adjust the focus tilt.
Is the secondary correctly placed in the tube centre? Check the spider lengths.

Now check the primary position and approximate alignment.
Place the tube horizontal and take a short walk.
Looking back at the scope, is the mirror central to the tube? It should be.
You are looking for concentric circles formed by tube and mirror.

Next, can you see yourself reflected? Probably not.
Some primary adjustment (using an assistant) will help align the scope machanical axis (tube) to the optical axis.
Yes I have seen scopes with main mirrors looking way off to one side!

At this point you are ready to look at collimation. Following whatever guide you find helpful.

Having got the big problems (if they are there) out of the way, you can be sure the scope is correctly assembled.
From one outing to the next you will find a glance down a Cheshire or a few seconds of laser will confirm alignment.
If collimation does change significantly, or often, you probably have a screw loose somewhere (no offence intended🤣).
Unless the tube gets a real hard whack, scopes hold collimation for a long time.

HTH, David.

 

Thanks David that’s really helpful! 
 

I’ll speak to Orion and follow these steps. 
 

sean

[Spile]

I’d recommend a Cheshire eyepiece for the secondary and a cap for the primary. The laser can be used to check and fix tilt and rotation errors but it will not identify offset errors. I’ve written a guide which you may find useful https://astro.catshill.com/collimation-guide/

[Steve Reed]

On 10/12/2022 at 21:24, Spile said:

I’d recommend a Cheshire eyepiece for the secondary and a cap for the primary. The laser can be used to check and fix tilt and rotation errors but it will not identify offset errors. I’ve written a guide which you may find useful https://astro.catshill.com/collimation-guide/

I can highly recommend this guide!

 

Steve

[wookie1965]

When I first got a Reflector many years ago I used "Astro Baby`s"  The method by Spile was unavailable to me at the time but is very very good. 

What I did use was this guide which simplify things into one step at a time without confusing reflections, https://web.archive.org/web/20200223041214/http://www.schlatter.org:80/Dad/Astronomy/collimate.htm