Posts Made By: Peter Rejto

I have an old Unitron focuser on my 5" f15 refractor. Some may be familiar with this focuser...it has a long inside threaded draw tube with an OD of 1 3/8". I don't know what the inside thread size is, but into this thread fits a reversible eyepiece adapter that can fit either 1.25" or the smaller size. The problem with this arrangement is that the eyepieces only pressure fit into the holder, thus heavier equipment, like a binoviewer, cameras, etc, bend down, or pull out. In addition the eyepiece tube itself is probably 2X as long as necessary (for the 1.25" eyepieces)., but perhaps necessary for a long barlow.

My question, does anybody know of an adapter that might screw into the draw tube directly (for 1.25" eyepieces) that is short and has a screw to securely lock in the eyepiece?

Thanks for any help!

I'm not sure I'm calling this by the correct name, but I'm speaking about the attachment that holds 6 eyepieces (1.25")that rotate around a central prism. I have a brand new one of these but it's giving me fits. There appears to be so much "slop" or free play in the rotating section as to render any sort of consistant alignment null and void. To test it I placed a piece of paper over the objective with the center of the lens marked and placed a laser in the eyepiece holder. Rotating the eyepiece holder the laser never returns to the same spot, and the difference in position is quite striking..up to 2-3" of change! I did this test because the first time I tried to use the attachment on my 5" refractor I immediately noticed that the diffraction ring pattern was totally off.

My question.... Is there a solution to this problem? Is my unit just defective? Have any of you noticed a similar problem?

Thanks for any suggestions.

Peter

Hello,

I'm feeling fairly frustrated. I'm in the process of rebuilding a 5" F15 refractor that I built up back in the mid 70s...Jaeger lens (and a good one at that!). I decided that my original large Unitron focuser was not up to the task anymore particularly since there was no way to secure heavy items in the draw tube attachment since there is no clamping mechanism, just slide in pressure. So I bought a really beautiful 2" focuser from Moonlite, that comes with a 1.25" adapter ring. Also have a 1.25" adapter ring from Williams Optics.

Problems start immediately when I have tried to use my 1.25" laser just to align the focuser with the center of the lens (never mind the cell alignment). The adapters fit so loosely into the 2" focuser that tightening the set screws, either to hold the adapter, or to tighten the 1.25" side around the laser, cause the alignment to the center spot to shift quite a lot from test to test. (The beam swings at least 3/8" around center.) I wrote to Ron Newman at Moonlite about this and got a swift response that "all" adapters are made to fit pretty loose, and that I ought to use a 2" laser with no adapter to align. Fine, I can accept that as reality, but why bother? It just means that anytime I would use any equipment, in any adapter...even a precision Williams 2" diagonal, or a 1.25" binoviewer, camera, I might as well have not bothered with the alignment! Most all of my equipment is 1.25" What does a person do here? I've thought of going to a machine shop and having a "tight" fitting 2" to 1.25" adapter made; at least if I had that adapter, and aligned with it, I could be sure of keeping some alignment. Or am I being overly fussy here? How do you all deal with this issue?
Sorry if this is old material...I'm kind of new here.