NavList:

The attached image is of a hand made Polaris/ Dubhe latitude tool (Latitude Wheeler) intended for emergency use and small enough to fit in the wallet. The Polaris corrections are based on the Q correction tables in Pub 249 vol. 1 epoch 2000. After 12 years the maximum correction has already changed over 2 minutes of arc. Dubhe is included for meridian passage and ex-meridian observations in the southern hemisphere.

The Latitude Wheeler is easy to make or just print out the image and correct with a current Q value from the latest Pub. 249 vol. 1.

Greg Rudzinski

[NavList] Re: Emergency Navigation Was: Black boxes in navigation Now:
From: Gary LaPook
Date: 13 Jul 2012 23:12
I don't see how Pythagoras can help you but the law of sines can but then you need a table of sines or a calculator. The rule of 60 does a good job up to about 35 degrees.for calculating the sine of an angle.

Polaris is easier to use than the sun because its declination changes very slowly and is now at 89° 18' so it is 42' from the pole. If you ignore making a correction for this you could still find your latitude within 42'. It is easy to make a correction for this by keeping in mind that polaris is lined up with the trailing star in Cassiopeia so visualize a line from that star to Polaris and estimate how far from the 270-90 position and estimate the correction.

gl

----------------------------------------------------------------
NavList message boards and member settings: www.fer3.com/NavList
Members may optionally receive posts by email.
To cancel email delivery, send a message to NoMail[at]fer3.com
----------------------------------------------------------------