[Laser] Re: Non-imaging optics - again

[J. Forster]

If you want to look at a small, distant source as in a data link, either a lens
or concave mirror is a much better choice. After all, the only light you really
want to collect comes directly from the source. Small, cheap lenses and mounts
are available as low priced astronomical telescopes. The only exception would be
a scattering path (over the horizon) links.

See, for example:  UNIVERSE 6 IN. REFLECTION TELESCOPE 900 mm  Item # 1950387811
on eBay. All you'd have to do is make a detector mounting adapter.

OTOH, the above has a pretty long focal length. Depending on your path length, a
cheap telephoto lens, such as :Tamron 400 F = 1: 7.5 Telephoto Lens  Item #
3000358774 might be a better choice. Cheap filters, tele extenders, and other
accessories are easily available. You can make a detector mount out of an
extension ring set and rear dust cover. Consider T mount lenses also.

You will need to match the focal length, detector size and path properties.

-John