Posts Tagged ‘Latitude’

10/06/2015 – Ephemeris – Deneb our home-town star

October 6, 2015 Comments off

Ephemeris for Tuesday, October 6th.  The Sun will rise at 7:46.  It’ll be up for 11 hours and 27 minutes, setting at 7:14.   The Moon, 2 days past last quarter, will rise at 2:36 tomorrow morning.

We, here in Traverse City, Michigan have a pretty unique relation to the bright star Deneb, as is any location near 45 degrees north latitude.  Tonight at 9:23  Deneb will be three-quarters of a degree due north of the zenith.  Due north means that it’s on our meridian, a line you may remember from your school days.  For astronomers it passes from the north point on the horizon, through the overhead point or zenith to the south point on the horizon.  Also due to our latitude Deneb is circumpolar, meaning that it doesn’t quite set on a clean northern horizon.  Deneb and 56 other stars are used for celestial navigation, which is still taught in case the GPS system goes down due to solar or enemy action.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Deneb nearly at the zenith

Deneb nearly at the zenith from Traverse City. Created using Cartes du Ciel.

Deneb nearly at the horizon

Deneb is close to the horizon due north. Created using Cartes du Ciel.

11/22/2012 – Ephemeris – Celestial navigation in the days of the Pilgrims

November 22, 2012 Comments off

Ephemeris for Thanksgiving Day, Thursday, November 22nd.  The sun will rise at 7:48.  It’ll be up for 9 hours and 19 minutes, setting at 5:08.   The moon, 2 days past first quarter, will set at 2:58 tomorrow morning.

Back in the days of the Pilgrims navigation was much less certain than it is today.  At the mercy of the winds and weather, sailing took a lot of courage.  Celestial navigation took the form of measuring the altitude of the pole star Polaris at night and the sun at noon.  That and tossing a log overboard attached to a rope with knots at regular interval to gauge their speed and progress.  That’s where we get the term knots as a measure of speed for nautical and aviation use.  Today we have GPS to tell us where we are.  However that is based on the position of not stars, but quasars, bright nuclei of distant galaxies, whose motions are currently too small to measure.  Have a happy Thanksgiving.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.



nasa-map_GPS Quasars

All sky map of quasar locations used as the celestial markers for the GPS system. Chart by David Bobolz, US Naval Observatory.

The chart above is from an article in the Telegraph.