NavList:

   

Reply

Regarding the "laser" beam

Bill you wrote:
"Is there any reason one could not dispense with the scope and use a
zero-magnification sight tube to take the optics out of the system?"

Frank replied:

"Yes, you have to focus the beam. Your worry that the telescope focus is
related to the index correction is wrong. Just to remind you, the whole
point of doing a "table-top" test of index correction is to take the human
eye out of the equation.

By the way, from my perspective, lasers are common-place. You can buy small
ones next to the candy at the check-out in any hardware store. The nice ones
with levels and on-off switches are in the back of the store. But if you
find lasers "exotic" or if they seem like a cheat (assuming you like to do
things in antiquarian fashion), then you can use any focusable light source
with a sharp image. For example, you could project a pattern of lines using
an old slide projector. I'm not saying that I recommend this --a laser is
the right tool for the job."

Frank

Agreed to some point, but I seem to be suffering from a generation gap on
the common usage of terms like "font" and "laser" that have been corrupted
beyond recognition.  Graphic artists/typographers with traditional roots
will understand my "font" reference.

Having played with real lasers over 3 decades ago, I just did not expect a
"laser" beam to have a spread on nominally 1/2 minute.  Figured the $30 to
$40 laser pointers for-sale at office-supply stores might be some dramatic
advance in technology (and off-shore manufacturing), and the $3-10 units in
hardware stores etc. some form of focused light.

Point being, I seriously doubt the lasers you refer to meet the standards of
both monochromatic and collimated light. Hence the need to focus these
b_astard stepchildren of a real "laser" beam.

Slowly understanding. 

Bill


--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply