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Another Eyepiece Question

Started by jadamslh, 01/03/2003 08:13AM
Posted 01/03/2003 08:13AM Opening Post
I picked up a pair of Zeiss eyepieces on Astromart for binoviewing. On the side it says: 46 40 42-9903 Kpl 10x/18, and: Zeiss West Germany. They have 1.25" polished barrels.
Can anyone tell me what these are?
Thanks
Posted 01/03/2003 09:11AM #1
You have a pair of Zeiss microscope eyepieces -- likely built with 23mm (.917-inch) barrels, subsequently modified (by owner, not by Zeiss) with 1.25-inch barrels for astronomical use.

The "pl" references "planokular." These are flat-field eyepieces (as most, if not all, Zeiss microscope eyepieces are).

The "10x" designation refers to their magnification factor when used with a standard (250mm focal length) microscope. Hence, yours are 25mm eyepieces.

The "18" designation refers to the eyepiece "field number," or field of view (field stop, actually). Yours have 18mm field stops.

I'm not sure of the lens design -- I'm guessing they utilize four elements in two groups, but I may be wrong. They are "orthoscopic," though not the classic Zeiss-Abbe design. The 18mm field stop yields around a ~42-degree apparent field.

Have you tried them, yet? Let us know what you think. I suspect they're superb (even if the fov isn't expansive). I have a newer T-coated Pl 10x/18 3-element aspheric, and it is absolutely fantastic. The eye relief's a bit extreme (long), but a foam eyecup solves that annoyance very nicely.

Perhaps another reader can offer a little better insight as to the lens design.

Best wishes.
-Dan