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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Index error adjustment...
From: Rick Emerson
Date: 1999 Jan 26, 11:56 EST
From: Rick Emerson
Date: 1999 Jan 26, 11:56 EST
Russell Sher writes: > Hi - With all the talk on sextants, perhaps I can squeeze in a question > about index error adjustment; > I have an instrument which has two right-angle shaped brackets for assisting > with index glass adjustment - With the instrument held horizontally, these > calibrating brackets are placed on the arc so that both the reflected and > true images are seen. The relative heights of these are adjusted into > co-incidence with the adjusting screw to give perpendicularity. When I > removed these brackets and eye-balled the arc directly, after performing the > adjustment, I noticed that there was still some error - In other words, > these two methods are possibly not as reliable as each other- OR is this a > case of parallax error, or the way which I am viewing the arc? Celestaire > (www.celestaire.com) market calibrating cylinders for the same purpose - > does anyone have any experience with these? Any comments etc. Without seeing what you're doing with the brackets, it's hard to suggest a remedy - if one's needed. We can talk about this off-list if you want. As to Celestaire's cylinders, save your money and get a set of dice from a toy store. Dice are machined to surprisingly close tolerances (or the results aren't random as they should be). Made of plastic, they don't rust and replacement costs are minimal. I keep a set in the sextant box for use as calibration tools and, if all else fails in reducing a sight, as decision-makers... [wink] Rick S/V One With The Wind, Baba 35 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= =-= TO UNSUBSCRIBE, send this message to majordomo@XXX.XXX: =-= =-= navigation =-= =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=