The mythos of Laser Collimation

[Macavity]

The TITLE is tongue in cheek - But in a genuine spirit of inquiry?

Can one really colimate a fast(er) Newt, when the laser calibration thingy flaps about in the eyepiece brass retaining ring like a... Unfortunately a suitable analogy escapes me! The documentation usually suggests that clamping the eyepiece (firmly) in ONE position will suffice. But is this *really* true? Maybe a self centering eyepiece holder at minimum?

For my sins, I persist (knowingly!) with my (video astronomy, small chip!) imaging 8" / F4. I am a keen follower (nay fan!) of "Ollygarchy" threads re. alleged Fast Astrographs! (I'm working on it. LOL) But it has caused me to review the whole validity of "colimation"...

At the moment, I'm working on getting things mechanically true - Squaring the (splendid!) focusser on my (budget) OTA. But is a typical (posh) LASER spot size really equal to the task of collimation? Even for F5 (F4.8) VISUAL Newts / Dobs (I know about "spotsize" too!)? Perhaps if I used (I do!) a "Cheshire" eyepiece?

I do have this radical thought that, for general use, collimation is (thankfully!) less critical. F5 Newt owners are simply "lucky" by being within budget-commercial mechanical tolerances. But are you truly confident that YOUR scope is properly collimated?

[ronin]

Someone posted a self centering adaptor for production via a 3D printer.

Looked pretty good and sounds as if that is the sort of thing you need.

Could ask round if anyone would print one and if cost effective make use of it.

[crashtestdummy]

Just get a hotech with the self centreing adaptor.works brilliantly

[Macavity]

Just get a hotech with the self centreing adaptor.works brilliantly

To their credit, they do seem to address the focusser "slop factor"

Thanks - Maybe that's what I'm looking for...

[Stargazer_00]

I use a HoTech as well but I don't use the SCA on it any more. I put it in the focuser and set it in place like I would an eyepiece. I don't want it collimated perfectly to the perfect centre of the focuser exit, I want it collimated to where the eyepiece centre will be when i put one in and that requires the laser to be positioned where the eyepiece will be. That seems logical to me.

I also set the focuser drawtube at about the point all my eyepeices find focus which is netiher fully in nor out, but close to 70% out.

[cotterless45]

Use a Cheshire or collimation cap to get collimated. On the night you can check using a Barlowed laser.

The laser should be checked for collimation. This will then get you spot on even with trusses that move and temperature changes.

A laser on it's own will just get you centre spot to centre of the 2ndry and not collimated on it's own. There have been sufficient posts pointing out the myth of lasers .Just use it as a checking night time aid,

Nick.

[Peter Drew]

Polaris is a very good collimating aid, cheap too!

[Macavity]

Polaris is a very good collimating aid, cheap too!

I am becoming a convert... Hence recent excursions into building an artificial star even...

An avid reader of SGL - More besides. The more I get into this stuff, the more "irreverent" questions I have?

I don't think the subject has been entirely done to death... I often wonder at the real validity of stuff I do.

[Stargazer_00]

I don't think my sky conditions have ever been good enough to collimate on a star, the airy disc is always instable. I highly doubt you'd be able to get perfect collimation every time on an F4 without precision kit and daylight and lots ot time.