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Posted by Robert May on October 18, 2003 00:48:34 UTC

The eye starts getting smaller about age 40 and finally gets to about 5mm at age 60 or so.
The only real problem with the .965 EPs is that they just don't have the FOV at the lower powers that larger diameter EPs have so I hope you understand that.
I'll also note, if I haven't already, that copyscopes really can't do the high powers as they are not setup as infinite conjugate focus but rather finite conjugate focusing operations and they tend also to be for monochromatic light sources which means that they are intended for focusing an image from one spot to another in the machines. As such, the focusing isn't as good when the source light is at infinity and thus you won't get the Airy Disc (the light spot isn't infinitly small bur rather is an area spot of some finite size with diffraction rings around it) and that the color focusing won't be perfect with such a lens as the lens isn't corrected for a full color rendition of the source as the light is just that green color that you see when the scan happens on a copier. Remember that when light hits glass at an angle, the various colors are spread out into a spectrum just like a prisim does and the problems with refractors is how well they manage to combine all of those colors back into one spot at the focus.

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