collimator

[oldnut]

just been looking at Cheshire collimators, very simple looking things which suits me. are they all much the same? I mean they cant get it too wrong I would have thought. are there makes that for some reason better than others?

[The BFJ]

I tried using a cheshire and found it trickier than it looks. In the end I bit the bullet and shelled out for a Baader laser colli. Much easier, but that's just my opinion. Not everyone seems to agree. What scope you got?

[Owmuchonomy]

I have both but I don't trust the laser because there is no way of collimating it. I got a Cheshire this week and it was so easy to use. However I haven't been able to test the collimation I did yet because of the weather. Astrobaby's site has the best instructions I can find for its use.

[Charic]

35mm film cap, laser and a Cheshire and I feel the Cheshire is more accurate. The laser can be imprecise during the initial collimation, but works fine used in conjunction with a Barlow for final check of the primary mirror. A Star test to confirm any mechanical adjustments.

My laser can be collimated, and is accurate to 15 feet and i see no rotation to the laser spot at this distance, but its possible to disturb the laser when inserted into the focuser tube during collimation of the secondary mirror. This is because of the fit of the laser scope in the focuser tube. I would still use all three devices.

[Martin Meredith]

I have both but I don't trust the laser because there is no way of collimating it. I got a Cheshire this week and it was so easy to use. However I haven't been able to test the collimation I did yet because of the weather. Astrobaby's site has the best instructions I can find for its use.

There are other reasons not to trust a laser, even if it is collimated (I refer to a single beam laser: on the other hand, a Barlowed laser, used for aligning the primary, is perfectly trustworthy). The reason that a single beam laser isn't good on its own for secondary collimation is that there are multiple ways to get the laser to hit the primary's centre, even if the secondary is rotated. I prefer to align the secondary with a sight tube, then use a Barlowed laser to align the primary, and finally, since I'm operating at F4, to use an autocollimator for fine tuning and to check everything is spot on. Typically I just use the autocollimator at the start of each session -- quite a lot of fun stacking all the reflections. And that's another advantage of the autocollimator: you can set up and check it during the day. It acts as a diagnostic/verification tool too.

Martin

[laser_jock99]

Having used various collimating devices the only one I can recomend so far is the Howie Glatter 2" collimator.  I collimate sucessfully F2.9 Newtonians with this device- other methods were not able to do this.

EDIT- not cheap I have to agree, but I can use this collimator on all five of my Newtonian scopes.

[dannybgoode]

+1 for the Baader LaserColli but would only use in conjunction with a sighting cap to ensure the secondary is rotated properly. 

The Baader is engineered to very tight tolerances and the laser is properly centred in each device individually.  The downside is that they are expensive - it is not cheap to make a good laser collimator.

I have a Cheshire also as you do not need to worry about batteries etc and it will always work.  I have collimated with the Baader and compared to the Cheshire and it was bang on...