Age old question for all reflector owners

[Nightshift]

What collimator to buy, Laser vs Cheshire

I have a GSO12" Dob that I move a lot and need to collimate regularly.

Now having an industry background in technology I like lasers, I read good and bad about them though, I like the one's with the return target (I think). Cheshire seems to be pretty foolproof but to me seem old hat and perhaps not as acurate, I think people that bag the lasers probably dont know how to use them properly??? Or am I just being geeky? Please only respond if you have first hand experience of both.

What would you buy assuming they are around the same price, ie. $69 - $120? .....and why?

[astrogeek]

I have both and use the laser to collimate the secondary and the cheshire to collimate the primary. If I were to buy again through I would probably buy the deluxe laser from BINTEL:

https://www.bintelshop.com.au/Product.aspx?ID=6737

This allows you to see the returning beam and therefore collimate the primary mirror as well with the laser. I have heard though that this may not give you correct collimation because for some reason a single beam can return to it's source even when the scope is out of collimation a little bit. From my understanding this could be remedied by inserting the laser into a barlow which would then create a slightly diffuse returning beam. Someone please correct me if this is not the case :). Anyway, I hope this has helped.

Leon

[ving]

i use a cheshire... dead easy and fool proof. I know that it is fool prof caue i am a fool.
I cant coment of lasers tho.

[janoskiss]

Laser is error prone, unless you get a good one. The inner workings of the Chinese units sold by most telescope shops are rather poor quality, and difficult to collimate because of the flimsy construction. The housing is good, but the way the laser is mounted and the laser itself are not. If you get a laser, get a good one.

Cheshire works well but when collimating by yourself it can be a pain to go back and forth between collimation screws and focuser of a large scope and trying to remember which screw moves the mirror which way. A good laser with a viewing window would help there, and you can always do a final check with the cheshire and an even more final check with star test. :)

[wavelandscott]

I have and use both...

I generally prefer the Chesire...simple no moving parts or batteries and I am 100% certain that it is correct. I use this as my primary tool. As ving says, it is "fool proof" and he is not the only fool around town ;)

I use the laser to "touch-up" or check after dark...mine has a viewing window so it is not bad as a one man operation but I am never as confident using it as I am with the chesire...

As I am basically a lazy person I truthfully only do "real" star tests when I have someone else veiwing with me...that way one can "twist" and one can watch...slack I know but at least I am honest about it...

I have not tried the "barlowed laser" technique but from what I read it is a good method too.

So in summary, get the Chesire...it is money well spent and a good one will last a life time...I got my Orion from Bintel...

[Miaplacidus]

I bought a Cheshire, and a friend gave me a laser collimator that he machined himself. The thing I would say about lasers is that their accuracy seems to depend quite a lot on how tightly it is fitted to your focuser. There is enough variation in focusers that it is impossible to generalize about how well it will provide accurate collimation in any particular scope. I might use the laser to collimate the secondary, but really I rely on star images to collimate the primary.

[davidpretorius]

a good chesire / sight tube and then star test.

[asimov]

I use no cheshire on my reflector, just the home made 2" sight tube for the secondary & star testing for the primary.

[janoskiss]

It's amazing how little you need once you know what you're doing. A film canister with a couple of peep holes and a bright reflective ring stuck on the end that goes in the focuser would work well too (or painted to highlight the centre: glow in the dark tape even better).

[Vermin]

http://www.iceinspace.com.au/forum/showthread.php?p=104023#post104023

http://www.iceinspace.com.au/forum/showthread.php?p=104226#post104226

[Miaplacidus]

You motorized your collimation screws????!!!!

Two questions:

1. Where'd you get that idea?

2. What drugs are you on?

[Vermin]

1. It's a Vermin original. Though there are similar systems around (e.g. JMI's big bino Newts have motorised collimation).

2. That would be telling. But seriously it is a fantastic time saver to be able to make adjustments looking at the returned ring binder shadow in the focuser tube and not have to walk back and forth to the back of the scope to make any changes.

The idea was also to be able to tweak the primary when looking through the focuser while doing a star test, but this has tuned out to not be required.

[RAJAH235]

I've used both but still prefer the Cheshire site tube. It's simple n drop proof.. Do star test to finalise if nec..... The Orion from Bintel is good value. :D L.
ps. Be careful if you buy the 'combo'. The X hairs are very fragile.
pps. It's always easier/quicker to collimate with 2 people..

[Blue Skies]

I prefer the cheshire. I've found it to be more accurate than a laser in smaller closed tube because it doesn't matter if you haven't taken the offset of the secondary into consideration.

If it was a big open truss-tube dob then a laser for the secondary for sure, with a cheshire for fine tuning on the primary.

And cheshires don't need batteries :thumbsup: although they do need a certain amount of light to work.

[Starkler]

A tip that I have found very useful.

Mark 3 lines on your centre donut that point in the direction of the collimation screws. It sure makes it easier when you have a visual cue as to which screw to move.

[janoskiss]

great tip Geoff!

[johnno]

I agree,
Thats a brilliant tip,well worth keeping in mind.

Regards.
John

[OneOfOne]

I have both. The first time I tried collimation, I just tried the Cheshire and fiddled for some time, but couldn't get it right. Then I tried the laser, I was able to get my wife (astronomical apprentice) to watch the red spot in the centre dot for the secondary and the return target for the primary. We got it aligned in a few minutes. Checked it with the Cheshire...spot on.

I would recomend both, the laser gives immediate feedback that anyone (wife) can understand, which saves getting up and down. The Cheshire gives confirmation that is not dependent on how well the laser fits, laser collimation etc.

[33South]

:rofl:

Thanks Brian, just choked on my coffee.

[astro_nutt]

I use both. I'll check the focuser to ensure no freeplay in it's movement. Followed by the Cheshire, then the laser. When all is done, I use a pocket mirror alongside the secondary to see the laser beam return to it's source and form a red "donut" around the exit hole. Then a final check with the cheshire. It's worthwhile to collimate your laser collimater every so often, cause they DO go out of whack!!!
A good cheshire will cost about $60, a Laser about $80+.

[Vermin]

The Howie Glatter laser I possess seems to hold it's axial alignment exceptionally well, but good point none the less.

It's pretty easy to test by rotating the laser in the focuser and checking if the return beam moves.

[Roger Davis]

The Cheshire (no crosshairs) will determine any rotation of your secondary.
The Sight tube (crosshairs) will determine axial tilt of your secondary, it will also aid in the collimation if you have a four vane spider.
The Autocollimator will set your whole system as close to a star test as is possible.
The star test will be the final tweak to get it spot on.