NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Bubble sextants on e-bay
From: Geoffrey Kolbe
Date: 2007 Jan 02, 08:56 +0000
From: Geoffrey Kolbe
Date: 2007 Jan 02, 08:56 +0000
Robert Eno wrote [NavList 1946] >I wonder if you would mind describing the Link A-12 illumination system for >me? Thanks for pointing out the interesting subtlety of the Mk IX bubble illumination system, so that the centre of the bubble is not illuminated. That had escaped me. As Paul Hirose pointed out, the A-12 does not have this sophistication. There is just a bulb in front of the translucent window of the bubble chamber. The brightness of the bulb is adjusted with a rheostat. While on the subject, it is worth pointing out that it seems to be important that the bulb has just a straight piece of wire as a filament, not a coiled wire filament as in most bulbs. Only the bulbs with the straight piece of wire seem to vary evenly in intensity as you turn the rheostat. Despite the fact that the centre of the bubble is illuminated on the A-12, I have had no trouble in shooting Polaris, which is a 2nd magnitude star. Geoffrey Kolbe --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---