NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Making an artificial horizon, and leveling thereof
From: Gary LaPook
Date: 2011 Jan 24, 21:55 -0800
From: Gary LaPook
Date: 2011 Jan 24, 21:55 -0800
"When life hands you lemons, make lemonaid." I just had a brilliant idea for you guys on the east coast that want to make a better artificial horizon. Put a bowl of water outside with some cover to keep the wind from rippling the surface. After it freezes the surface should be level. Remove the cover and use the frozen surface as your artificial horizon or place a mirror on top of the ice and it should also be level. An easy way to practice with an artificial horizon is to take a number of observations to allow you to determine your accuracy is to use the meridian transit of Polaris. When Polaris is crossing the meridian it is moving horizontally and its altitude doesn't change. For the period of more than 15 minutes both before and after meridian passage the altitude of Polaris changes less than one - tenth of a minute (0.1'). For a period of 34 minutes before and after passage the altitude of Polaris changes less than one half minute (0.5'.) For 48 minutes before and after its altitude changes less than 1 minute. Calculate the time that Polaris is crossing your meridian and get out
Now is a good time to shoot Polaris with an artificial horizon as it is crossing your meridian about at a bout 6:30 p.m. so its altitude doesn't change even by one tenth of a minute for about a half hour so you can take many shots and don't have to compute a different Hc for each shot. Here are some links to my prior posts about this technique. http://www.fer3.com/arc/m2.aspx?i=111363&y=200912 http://www.fer3.com/arc/m2.aspx?i=111364&y=200912 This is a link that provides the time that Polaris is crossing your meridian. http://www.cadastral.com/2011jan.htm gl --------------------------------------------------------------------------------------------------- --- On Mon, 1/24/11, Fred Hebard <mbiew@comcast.net> wrote:
|