Which type of Collimator?

[Moonshane]

Nice post mate, but could I just add here, and this seems to be the main bone of contention when people read AB's guide (she doesn't mention the centre spot at this point and just stresses the importance of getting all 3 clips in view), is that all 3 or 4 of the primary clips do NOT need to be visible for you to be properly collimated. As long as your secondary is showing a circle directly under the focuser and the crosshairs of your Cheshire are on top of the centre spot you're axially aligned, having all 3 clips in view just means you can see the full reflection of the primary thus gain the maximum light.

That's my understanding anyway, but please feel free to correct any duff info...

you are quite right - although the reference to clips is just to ensure you have the secondary roughly aligned with the primary. you then tweak the alignment with the adjusters on the secondary. you don't have to see all clips but you should have any view of them sat equally around the view - if this makes sense - as I say it's so much easier to show than tell.

[Jason D]

If the secondary mirror is precisely aligned under the focuser

and

if the cross-hair of some quality sight-tube is precisely aligned with the center spot

then

Why would you see few clips and not all?

Ideally, you want the primary mirror reflection outline to coincide with the secondary mirror outline with all clips showing in addition to aligning the cross-hair with the center spot.

See attachment.

[earth titan]

I agree. All clips should be visible if the secondary is aligned properly.

If you have a long Cheshire rather than a collimation cap though, sometimes none will be visible. Hence the benefit of a collimation cap.

Typed by me, using fumms...

[lestergibson]

When I first had to collimate, I found it tough just trying to make sense of what I was seeing through the collimator. I found this tip on quite a few threads; put a sheet of a4 paper into the ota opposite the focuser tube (draw tube?). I did that and found that it really helped to clean things up. Now I look into the collimator and wonder why I had problems in the first place but there you go. Just thought I'd mention it in case it hasn't been before.

[Tinker1947]

I have a chesire which i used for quite a while, then purchased a baader MkIII laser, there not much difference the Baader is a tiny bit more accurate, its also quite a bit quicker as on my 1200mm FL i can see the laser in the center of the Baader while turning the adjusters on the Primary in day light or night time, the Baader also checks out 100% when put in a 3 jaw chuck on a lathe the beam is static at 12' when the chuck is turned....

[pat]

I'd like to add a differance view to the use of crosshairs. They are overrated. They tend to be too thick, making it difficult to see the cenral spot on the primary. They are fussy when looking down the cheshire making accuracy questionable (Also there is the reflective secondary crosshairs to take into account). I first used a Tectron Cheshire. But was told I needed a combinatin one with crosshaires. I had the same problems listed above that was posted by other members in this fourm and others. Some members have cut out both crosshairs. I read that by leaving one, you can align it with the vertical spider vane and the one crosshair should pass through the center area or portion of the secondary. Pat