Laser collimation blurry on an old scope

[Gomtuu]

I have been passed an old Meade 4.5" reflector with goto and thought it would be useful as a backup scope.

I have a laser collimator which I used to collimate my 200PDS, so I thought it would be a simple matter to use it on the Meade. However, when I put it into the eyepiece, the dot on the primary mirror was a diffuse spot about a centimetre across. By the time it comes back to hit the target on the collimator it's a diffused 2cm glow. There appears to be a lens in the bottom of the EP focusser, which I am guessing is what is causing the beam to spread. I can't focus the beam down to anywhere close to a point.

I suppose my question is, is this normal for a scope of this type and if not, what do I need to do about it?

[umadog]

That thing doesn't seem to be listed in the manual: http://www.meade.com/manuals/TelescopeManuals/Reflectors/Meade4500.pdf

I don't know what it could be. It can't be necessary. Why not remove it?

[Gomtuu]

It's a Meade DS-2114S if I'm reading the spec correctly. I've got a manual but it gives no indication of what is going on in the (wobbly) focusser.

I'll try your suggestion of removing it if it's possible.

[Gomtuu]

Ah, according to another forum, it's apparently a Bird-Jones design and the lens is a corrective lens to "reduce or eliminate the inherent spherical aberrations of the primary mirror".

I suppose I had better leave it in place!

[umadog]

Ah, good! you got it! I just realised that too and was about to let you know. Hope it work out.