View Full Version here: : best collimating tool for a newtonian.
01-12-2010, 07:28 PM
hi . i have just taken ownership of a 8" newtonian and I would like some advice on a collimating tool.
I will be using it mainly for visual use but i may want to use it for imaging sometime later, so i need to get something that will collimate it accurately enough for imaging in the future.
what is good to use here.
i was looking at the 1.25" howie glatter barlowed collimater.
will this be a good one to get?
i know nothing about collimating . have never had a reflector before, just refractors, and a mak.
01-12-2010, 07:46 PM
I have an 8" newt and use catseye gear. It's fantastic.
01-12-2010, 08:40 PM
Catseye for me. Doing it the old fashioned way, you learn so much more about what you are trying to achieve.
Will probably cost about the same as a laser, but it is infinitely more capable.
Jim gives you all the details on what to do in the pack. Took me a few goes to get it right. But now it is a piece of cake.
01-12-2010, 09:16 PM
If money is no object :D, and you want perfection :thumbsup: you'll probably spend more than you did on the scope!
If the scope has a 2" focusser:-
* 2" Howie Glatter laser with barlow
* Three 2" Catseye tools - sight tube, cheshire and dual-pupil autocollimator
Sight tube followed by laser followed by iterating the cheshire and autocollimator.
However these tools may exceed the engineered capability of your scope due to slop, flex, mirror movement etc.
01-12-2010, 10:37 PM
so is a common laser collimater adequate for visual use?
It will get you in the ballpark for sure, but the more expensive tools will give you a new perspective on it and as Eric correctly points out, will start to highlight the limitations in your scope.
I've got the Catseye INFINITY XLK Autocollimator and the TELECAT XLS. The TELECAT is a combined sight tube and Cheshire in one unit. They are both very good.
The Howie Glatter is also supposed to be very good.
You could always go 'commando' and use a star. Whatever you do, don't ask for advice on CloudyNights - it seems to be a touchy subject over there.
04-12-2010, 09:47 PM
I found a common laser collimator plus a cheap 2x or 3x barlow gave quite reasonable results on my 8" f5 newt. The barlowed-laser bit is the key. Do a google on that and there are some threads here too.
04-12-2010, 10:12 PM
I'm old school, so I'll stick with my 2" sight tube (costing about 2 bucks) for the secondary, & the star test for the primary.
04-12-2010, 11:14 PM
That is something that I've always thought about. Wouldn't the high accuracy of an autocollimater be moot if flex/slop etc are put into the equation, which lets face it affects more or less every telescope to some degree, particularly truss tubes?
04-12-2010, 11:58 PM
Not necessarily, depends on what the flex/slop is and whether it is repeatable. In my case I could collimate perfectly with a catseye xlk but when I imaged things were skewed. Then I was fiddling around collimating one day and noticed severe movement in collimation when I tightened the compression ring (previously I had collimated with everything untightened like the book said).
What i found though the amount of flexure when tightening the compression ring was always the same, now I collimate with it tightened and all goes well.
05-12-2010, 10:39 AM
With just a standard laser you can get incorrect results. You cannot use the standard laser to adjust the tilt or axial positioning, or rotation of the secondary mirror. With an incorrectly set up secondary mirror it is possible to adjust the primary mirror so the telescope appears collimated, when it is not. A laser device barlowed or otherwise is really only capable of adjusting the tilt of the primary mirror "after" the secondary mirror is properly set up. For this purpose it is an excellent tool. For a newcomer to properly collimate the telescope from scratch you need some form of sight tube device. If you are only going to have one collimating tool the cheshire/sight tube tools are your only option IMO. In this regard the catseye is excellent. The various combination cheshire/sight tubes work well also but not to the accuracy level of the catseye tools.
05-12-2010, 10:45 AM
Catseye set it is - accept no substitute. :P
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