[visionlist] Roman acuity test?

[Gislin Dagnelie]

Denis,

Whether it is true or not, I think most of us would not be very impressed with a two-point resolution of 12 arcmin.

Unless, of course, the 12 arcmin is the separation of Alcor and Mizar in 2007, and their separation has increased over the past two millennia.

Constellations are known to change shape through the ages as our terrestrial vantage point in space shifts due to parallax.

You may want to check with someone in the Astronomy department to figure out what the real acuity measure was.

Gislin

P.S.  A Roman centurion commanded a group of 100 men, so he would be equivalent to a captain or so.  The term "centurion guard" does not ring a bell with me in a Roman context, but the term is used in World of Warcraft... Maybe that's where they use this acuity test?

>>> Denis Pelli <denis.pelli at nyu.edu> 08/04/07 2:33 PM >>>
Reading various posting found through Google, I think the following is
true:

"The Roman legions required each candidate for Centurion Guard to
resolve a pair of stars, Alcor and Mizar in Ursa Major, 12 min arc
apart."

However, I would like to publish this in an article. Can anyone specify
a reference that I can cite for this fact?

Denis Pelli
Professor of Psychology and Neural Science
New York University
http://psych.nyu.edu/pelli/ 

p.s.
Were Centurion Guards lookouts?