NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar Distances with Alex's SNO-T
From: Bill B
Date: 2006 Nov 13, 00:12 -0500
From: Bill B
Date: 2006 Nov 13, 00:12 -0500
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 -~----------~----~----~----~------~----~------~--~---