Re: ATM Foucault Test

["Bob May" <bobmay@nethere.com>]

The light as it approaches the KE from either zone is going to hit the KE at
the ROC at the same time.  The problem that you run into is that you have to
SEE the light after it leaves the KE from both sides of the mirror mask.
This means that your eye, which may have only about 2-3mm of opening, has to
gather in both of the beams of light after it crosses the KE edge.  If your
eye isn't close enough to the KE (a F4 beam will have to have your eyeball
less than 8mm from the KE in order to gather the light from both of the
zones at one time and that is quite close to be to a sharp edge!) then you
will see either one or the other of the edge zones.  For an example, take
and let the KE be well off from the ROC point and step back a bit from the
KE.  You will see the mirror won't be as fully illuminated by the source
light.  This is because all that your eye is seeing is that part of the
reflection that fits into your eye.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net