Re: Ancient Viking ATMers

[Dwight Elvey <elvey@hal.com>]

"Justin Kelly" <iustus@home.com> wrote:
> 
> http://news.bbc.co.uk/hi/english/sci/tech/newsid_702000/702478.stm
> 
> The vikings are now recognized as having lenses. Once thought to be
> ornaments, they have been tested and are of exellent quality. They are
> eliptical, best exanple being 2 inches in diameter and one inch thick, and
> made of "rock-crystal".
> 
> The article title suggests that they could have been used as telescopes, but
> I am curious whether or not such an extremely convex lens really be useful
> for Astronomy, or any long distance viewing at all? Perhaps they were just
> used for starting fires. However, if anyone had the need for a telescope at
> that time it would be the ocean navigators like the vikings.

Hi Justin and all
 It would be interesting to know the f/ratios of these lenses.
Large f numbers don't make good fire starters small f numbers
work well. Large f numbers make good telescopes. Small
f numbers make good magnifying glasses.
Dwight