NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Children's land-locked "Sextant"
From: Bill B
Date: 2007 Nov 28, 02:57 -0500
From: Bill B
Date: 2007 Nov 28, 02:57 -0500
> The Davis Mark 3 sextant runs about $35 and would be good for a group > of kids to get their hands on. Since there are no optics, it is pretty > easy to line up the suns image using an artifical horizon. > > I blieeve Omar Reis on his web site shows how to make a sextant out of > a CD. I am familiar with Omar's CD sextant. Celestaire offered a "build it yourself" cardboard sextant and optional bubble horizon at a very attractive price. (By all means splurge for the bubble if landlocked.) If assembled and used carefully, this unit(s) will provide consistent results that are better than advertised. I am good to plus/minus 3 minutes of an arc with it (including using the optional bubble horizon) on a regular basis. For the anal retentives: Upsides --Inexpensive. --Very useable bubble horizon, can be lighted easily from above. --Vernier scale easy to interpolate. --All but index error adjustable on the spot by bending the cardboard a bit. Downsides --Requires care in assembly. --No horizon filter(s). --Not suitable for a wet marine environment. --Front silvered mirrors (actually polished stainless steel if I read it correctly--are identical in size. NOTE: This eliminates the need for glass on the see-through side of the traditional horizon mirror as there is no refraction to cope with. However, due to distance (index mirror smaller via perspective) there is a gap that makes aligning stars or the horizon a pain in the a_s without bending the cardboard frame and introducing other errors. As a designer--or if I were to build another--I would adjust sizes or shim one so I had an uninterrupted view between the horizon and index mirrors. Bill --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---