what collimation tools do you use?

[monoxide]

not a 'how do i collimate' thread, i'm more interested in what tools people are using to check/adjust their collimation and how accurate they think the results are.

i've always just used my cheshire but i've never felt that i absolutely nailed it, especially when it comes to imaging.
i did use a laser collimator for a while but in the end all i found it useful for was checking the secondary, it got me in the ballpark for the primary but i always needed to tweak with the cheshire.

whats your angle of attack? lasers, cheshires, sight tubes, autocollimators, barlowed lasers? and how confident are you that your getting close to perfect when the jobs done? (example: i know my collimation varies a bit with my 12" because i can see the difference at the eyepiece occasionally)

[dazastar]

I first tuned my laser with a perfect collimated cassegrain scope (most laser collimaters are out themselves).

Then after laser collimating my dob, I use the cheshire. After that I use the star method where you put a good bright star out of focus and line up the consentric circles. This does take a bit of practice but easy to learn how to do. A nice medium to high powered wide field ep can help too, changing powers between them till you notice stars having comet tails - then adjusting the collimation screws till the stars are all pin point (dont do this unless you have really good seeing).

Hope this helps - anybody got better sugestions I too would like to read them as I myself am still only a noob (got my first scope in 2005) and still learning.

[dannat (Daniel)]

I use a sight tube that i made by throwing away the glass from a terrible 4mm cheap ep. It fits very well in the focuser and the small hole lets me clearly see the secondary & primary alignment. It probably isn't that accurate but the scope see's ok.

[Starkler (Geoff)]

Originally Posted by monoxide

i've always just used my cheshire but i've never felt that i absolutely nailed it, especially when it comes to imaging.

One thing worth being aware of is that factory placement of primary mirror center spots is not always accurate. If you doubt the accuracy after careful collimation with a Cheshire its worth checking that your centre spot is indeed in the center.

Originally Posted by dannat

I use a sight tube that i made by throwing away the glass from a terrible 4mm cheap ep. It fits very well in the focuser and the small hole lets me clearly see the secondary & primary alignment. It probably isn't that accurate but the scope see's ok.

What you are describing there is often described as a "collimation cap" collimation tool. A "sight tube" tool has crosshairs at the end to facilitate secondary alignment.

As for me, I just use a cheshire combo tool. I have a synta 1.25" and a catseye 2" telecat. I see much raving on CN about the catseye tools but IMO theres nothing magical about them except that you get the center spots that fit the cheshire viewing ring, which is important to get an accurate alignment.

[erick (Eric)]

If I was starting from the beginning:-

1. Orion Cheshire/Sight tube - used solely as a sight tube to adjust/check secondary mirror is centred and "round". Once set, it has not moved on either GSO scope.

2. Bintel (GSO) laser to adjust secondary tilt and primary tilt. (Check laser collimation occasionally on a "V-block", certainly after battery change. Have added a layer of "Contact" to the laser barrel to ensure a snug fit in the focusser.)

3. Barlow the laser (GSO 2x or Televue 3x) to check reflection of shadow of centre spot is centered at focusser. (It always is.)

4. An Andrews Cheshire collimator (again a layer of "Contact" to the barrel for snug fit) to do a final check. (It is usually spot on after 1, 2 and 3 - and even after just 2.)

5. What's the stars look like? - focussed and just out of focus, either side.

I am learning how to use an autocollimator and may add that at one stage, but I'm not sure the mechanics of the GSO dobs are really up to this accuracy/precision - eg. the laser return at the focusser in step 2 will move slightly as scope is elevated from horizon to zenith.

Usually, I will only do steps 2, 4 & 5, unless I have a particular concern. I've found I can bounce the OTA in a trailer over general highways and side roads without much loss of collimation.

Of course, my needs are visual, not imaging - I think I can tolerate less than perfect collimation.

[monoxide]

hmm,
i have been thinking about getting the catseye tools but it seems like a lot of money for something that may not be needed.
even though my collimation may not be absolutely perfect with a cheshire, do you really think its worth the extra money for that little final tweak?

[Screwdriverone (Chris)]

1) Sledgehammer - dont laugh, it almost eventuated.

2) If 1 fails, a cheshire and then my eye on a star test outside.

Cheers

Chris

[GrahamL]

I use my eye down the draw tube to rough align then an andrews chesire with broken cross hairs and never have a problem ..I have a skywatcher ( Ithink it is ) cheshire sight tube combo and have grown to completely disslike and won't use it anymore.

[CoombellKid]

Had a laser collimater (unbarlowed, they're a bit useles really). Then a home
made collimation cap and used that for several years. But the last and best
IMO is the Celestron Chesire (long nose) I brought a couple of years ago
at Astrofest QLD, it's all you need.

regards,CS

[CoombellKid]

Originally Posted by Starkler

One thing worth being aware of is that factory placement of primary mirror center spots is not always accurate. If you doubt the accuracy after careful collimation with a Cheshire its worth checking that your centre spot is indeed in the center.

Geoff,

Thanks for the heads up, I just wrote a note on the box storing my 16" to
check that before I load it in the scope

regards,CS

[CoombellKid]

Originally Posted by Screwdriverone

1) Sledgehammer - dont laugh, it almost eventuated.

Chris

Well I suppose if you hit it with just the right force in just the right places
I dont see why you couldn't.

regards,CS

[White Rabbit]

I'm a complete n00b at the collimation business but I just bought this one from the US. The reviews that I've read have all been very good.
http://www.astrosystems.biz/laser.htm

ATM, I have the orion collimation eyepiece. But I have pretty bad astigmatism so it's had to use for me.