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Andrew,
I recently had the opportunity to use an Andrews (BC's) and Orion (mine) collimating eyepieces side by side. The Orion is a classic Cheshire assembly plus sight tube with crosshairs (1mm wire)mounted in the bottom of the tube 120mm from the peep hole. The Andrews is similar except it is only half the length (or even a bit less) and the crosshair wire is thinner. With my 48yo eyes I could not "see" the crosshairs in the Andrews unit. In the Orion unit the crosshairs are still inside my focal range but they are still sufficiently focused to be useable. If I use reading glasses, I can see the crosshairs OK but then the mirror centre marking becomes very blurred...........sigh!! Even with reading glasses I still found the Andrews unit almost unusable for me.
BC might have some additional comments on this.
Cheers,
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