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rocketandroll

Collimators - advice from those who've used them?

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Hi all

yes, another collimation/collimator thread... I did go back and read a few earlier threads however wouldn't mind some direct advice fom current users...

I'm getting my first reflector (an Orion Optics VX8L at f6 with uber-shiny 1/10thPV optics) delivered next week... I have only used frac's up until now... so have never attempted collimation.

I intend to buy at least one more faster reflector after this.

I want to buy a collimator, learn to use it right, and not have to buy another one to get accurate collimation of a faster scope in future...

I have looked at the Bader and HoTech lasers... also looking at Cheshires....

what would people recomend given A: I've not done it before and B: my future needs?

Thanks

Ben

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The laser is the easiest to use for a first try, with the following caveats:

1. The primary must be centre-spotted (with a paper ring stuck exactly in the centre). If that hasn't been done by the supplier you will have to take out the primary and do it yourself (it's not a difficult task). Then you'll definitely have to collimate after re-assembly!

2. The laser collimator itself has to be collimated. This can be tricky - I gave up on one laser because I simply couldn't get it right.

So, if not the laser - the Cheshire comes next. More accurate than even a properly-collimated laser, from my experience. Not quite so easy or intuitive to use and you need ambient light - preferably daylight. It's worth paying for a good-quality Cheshire rather than making your own collimation cap.

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Had the Baader and it's not too bad but it did need colimating first as it was a bit off.

The Hotech simply doesn't need colimating and the self centering adaptor also makes it more accurate. It uses a cross hair laser beam instead of the sort of round blob that most others have which makes it much easier to use. I've used it on scopes up to f/4 and it's a doddle even with such a fast scope.

Some people get on with Cheshires and some don't. I've used both and the find the Hotech just so much easier to use and I can get collimation spot on in under a minute.

John

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Hi Ben

I have a laser colomater here if you want to try one out before you buy.

I can also run through how to use it with you as well.

Graham

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Cheers all

The HoTech is looking tempting, the cross hairs just makes sense as you can see where it is even when it's almost bang on center. At £120+ with the 2" adapter it ain't cheap... but as I said, I do want to get ONE collimator.

I learnt that lesson with the guiding thing :-) Now I have a £300+ Lodestar... it's a doddle.... should have splashed the cash in the first place and bought the right product... which is why, if people have good experiences with them, the HoTech is top of my list at the mo.

And thanks Graham... would be good to have the assistance first time out... don't want to loose any clear nights messing about with it... maybe if you're free one day/eve next week we could meet up and have a stab at it? I'm told by John at Orion that the f6 VX8L is a doddle to collimate because it's that much slower than the f4 and faster imaging Newts.

Ben

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A laser must be well collimated, which it should be when you get it. My Baader was. However simple use of a laser also requires that the focuser is collimated and that the laser is tightly and correctly aligned in the focuser. If all this is true then laser collimating is unambiguous, quick and simple.

A Cheshire is less intuitive to use, but not difficult to learn and in a sense it is a better tool for the job, because it does not have the alignment sensitivity that a laser does.

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I bought the entire Catseye kit (sight tube, Cheshire, AutoCollimator) and am very happy with it (12" f4.9 Dob). I use the sight tube (or just look down the naked focuser) and the cheshire every time i haul the beast out. With the red reflector triangle they provide it is very easy and intuitive.

I use the autocollimator only periodically, 3 to 4 times a year to fine tune the collimation. It is not as intuitive, but I had the hang of it after 2 or 3 uses. Catseye has the Rob Morrow book on collimation...very helpful. I say this because if you are looking into only buying one for future, faster optics, consider Catseye. A bit pricey but worth it, IMO....check out the website, lots of good information.

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Having progressed/sunk to an 8" Dob, would recommend a sight tube for setting the primary and Steve Smallcombe's Rear View Barlowed Laser Collimation ststem which works.

If an idiot like me can cope, the intelligentsia of this forum such as your good self, will find it a doddle.

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I use a cheshire for the secondary and the barlowed laser method for the primary so I don't need to worry about collimating the laser. I will one day invest in the cats eye kit though as it seems to me to be the most accurate method.

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Hi Ben,

If you can only get one tool, then get a decent Chesire Eyepiece & Sighttube, as it will allow you to do everything.

However it isn't at first the most intuitive tool there is. For sheer ease of use you cant beat a laser, but even a Hotech has its limitations as regards accuracy.

If you plan to be with reflectors for a while, then I would recommend a Catseye setup and a Hotech laser.

Good collimation is very important, simple with the right tools, and something worth investing in.

If you are around Coventry I can show you these bits, just pm.

Cheers

Tim

Edited by Tim

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I use non-powered tools myself. Lasers are OK but I never really trusted them (I has a relatively cheap but well collimated one).

I use a basic collimation cap (home made) to do the initial collimation check on the secondary - this almost never needs adjusting. If it does I use a Cheshire with the 45 degree plate obscured and only the cross hairs showing to adjust the secondary.

I then use a cheapie plastic Cheshire with no cross hairs to find tune the primary.

Works for me even on f4 scopes and cost less than £30.

The thing with collimation is it's very easy once you see how it all 'fits together' and you can take it as far as you want. the primary is the critical thin for visual observing but you need to be more accurate with photography or with very fast scopes.

Don't fear it.

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A sight-tube is for adjusting focuser axial alignment (via the secondary mirror). The first pass of a laser does the same thing with equal accuracy (assuming laser is collimated).

A Cheshire is for adjusting the primary (primary axial alignment error). This is the same as return beam of a laser. Both are equally accurate (if made well and collimated) since both are based upon two passes of the tube. You will find confusion regarding what a Cheshire is, since they often come with a sight-tube attached and that has the cross hairs needed to adjust the secondary. A Cheshire proper is the same thing as a "collimation cap" with a shiny surface. Both tools are for adjusting the primary. A barlowed laser is to be preferred for primary adjustment since in this configuration it doesn't need to be collimated. Tublugs are tools that do this rather nicely.

Finally there are autocollimators, which are rather like Cheshires but have mirrored inside surfaces. These tools allow up to 4 passes of the light beam and so are the most accurate things going.

There are various Cheshire designs out there. After some messing about, I have chosen to use the Catseye Cheshire, sight-tube, and auto-collimator. These are used in combination with Catseye's centre-spots. When used with the correct centre spot, it's easy to get very accurate results with these Cheshires. The autocollimator is an amazing tool, providing a lot of information, and is very accurate. Also, it doesn't go out of alignment. You can use a red LED clipped to the spider to collimate in the dark.

CATSEYE Collimation Main Page Frameset File

If you want to do it right and have a 2" focuser then use 2" tools. Don't go the route of using a 1.25" tool in an adapter. Here are some useful links: Rob Campbell's Home Page

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Hi Ben.

No problem we can get together and go through it any time you like.

Let me know whats best for you.

Graham

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Hi,

I bought all the Catseye kit but I would just get the Autocollimator and the Astro Engineering 1.25 Collimator as it gets you near enough to use the Catseye.

Cheers. Andrew.

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The Antares one I has came way out of collimation. Lined it up best I could and got rid of that in favour of the Howie Glatter which is superb.

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I had a Baader Mklll laser but now use a Cheshire/sighttube exclusively. I find it every bit as accurate and easy to use as the laser. One thing that puzzles me with the Hotech is that although it is perfectly centered in the focuser, when the eyepiece is in the focuser it is offset by the retaining screws or ring. Some may say that small offset will not make any difference to the collimation but i noticed that even the slightest movement of the laser caused quite a shift in the beam position.

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