19c465d2   
   From: me@here.com   
      
   In article ,   
   Shay Ghilai  wrote:   
   >   
   >Hi there,   
   >   
   >We are looking for a =91zero power=92 meniscus, made of glass or plastic   
   >(Clock glass).   
   >   
   >Thickness:      Approx 3 mm   
   >Radius of curvature:    Approx 500 mm   
   >Diameter:               120 mm min (If larger, we=92ll cut it to size)   
   >   
   >Seen with unaided eye, it should look smooth, no waves or ripple, for   
   >both transparent and reflected light.   
   >Low cost off the shelf.   
   >   
   >If coated, OK too, we=92ll remove coating.   
   >   
   >Eventually, it will be used as a simple off-axis collimator.   
   >   
   >TIA   
   >   
   >Shay Ghilai   
   >   
   >sgoptics@netvision.net.il   
   >sgoptics@gmail.com   
   >   
   >   
   >   
      
   I would check with a commercial eyeglass lab. They have all sorts of "blanks"   
   in dim. of the sizes you're looking for, very good quality, and usually very   
   inexpensive. I had a need for very large negative cyl. lenses years ago, I   
   think I paid about $5 USD per lens for an order of 10, just a fraction of   
   what an optical supplier would have charged if they could have even supplied   
   a very low power, large diameter optic.   
      
   good luck!   
   D.   
      
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