homemade lens

The Lens

Once again, theoretical design ran smack into the realities of amateur lens building. I simply didn't have a positive meniscus lens in the required focal length and diameter, and there wasn't anything suitable available from Surplus Shed. My only choice now was to complicate things even further and use three elements rather than two. Instead of a having a rear element made from a single positive meniscus, I found a combination of two positive meniscus lenses (+66 and +140) that gave me what I needed. In front of that combination, I added a nice 10-blade iris from an old Ilex shutter. Up front, I added a -105 negative meniscus which I was able to adjust so that the lens came to focus at infinity exactly when the focuser was fully retracted.

Here's a view of the completed monster.

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