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Hi Rod,
I suggest you hunt around for a 2nd hand Televue type 1 Paracorr. These are the best for visual observing. There are 3 different versions of the type 1 paracorr. The first was non adjustable, avoid it. The 2nd was adjustable with single locking screws. This works just fine. The last of the type 1 paracorrs has double locking screws on all the adjustments. This is the best one mechanically but both of the latter type 1 paracorrs work just fine down to F4. I have both of the later type 1 paracorrs, the newest one is a touch nicer mechanically but they do the same job optically. The original non adjustable paracorr isnt as good as the later versions and should be avoided IMO.
There are conflicting opinions on whether the paracorr "steals precious photons". On the central axis you certainly dont need it. About 30% or further from the central axis the paracorr will allow you to see dimmer stars than without in scopes faster than F5. I dont need to go into the physics of why that is in this thread but take it as a given. There is plenty of literature out there on why this is. If you are only worried about observing targets in the centre of the FOV you are better off with simple minimum glass narrow field eyepieces like orthos and plossls and no paracorr. If you are going to use 60 degree plus eyepieces and use all of the FOV and your scope is faster than F5 you are generally better off with a paracorr and you will certainly see dimmer stars and features than without a paracorr the further off axis you go in sub F5 scopes.
Cheers,
John B
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