See if you can find a 75 mm diameter +1.0 Diopter eyeglass lens and a 75 mm diameter +0.75 Diopter eyeglass lens. CR-39 plastic is okay, but anti-reflection coated glass would be better. You can ask an optician in a small eyeglasses shop to supply these. Tell him or her they are for a projection lens, so you need them as large diameter as possible, uncut, and not mounted in any frames. Cost me $30 US for uncoated plastic.

Then you find a 60 mm long piece of plastic pipe with inside diameter just over 75 mm. (I use ABS sewer pipe from a home improvement store.) You can CAREFULLY cut 3 mm wide rings from a large paper mailing tube to make heavy paper retaining rings, or you can cut them out of some more of the 75 mm ID pipe. Cut a section out of the retaining rings so they fit snuggly inside the pipe. Then use pairs of retaining rings to mount one of the lenses at each end of the tube, with the convex curves toward the outside.

You just made a 585 mm symmetric duplet. Should be close enough. You can experiment with distances shorter than 60 mm to get the focal length closer to 571 mm.

Sounds like Guy Grotka wrote that? Yes it will work but it may have a limited field of view. I always wanted to try a pair of color corrected duplets sold at SS but never got around to it.

DJ

Field of view shouldn't be a problem with 75mm diameter lenses, as long as the tube is the same length or shorter than the diameter of the lenses. A 30 degree field of view with that EFL should work fine.

What is described in the quote is a duplet projection lens, but it isn't a symmetrical duplet. Symmetrical duplets use two lenses of the same diopter or focal length. He uses two different focal lengths.

A good online source for the positive meniscus lenses to use if you want to try this is Rolyn Optics . They have reasonable prices for simple lenses. If you want to experiment with this before shelling out almost $17 per lens (for the glass ones, $9 for the plastic), go to your local drugstore and snag a pair of "Reading Glasses" with the diopter power you want, pop the lenses out of the frames and start experimenting.

Tgreenwood