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07/14/2023 – Ephemeris – Finding Polaris and why it’s important

July 14, 2023 Comments off

This is Bob Moler with Ephemeris for Friday, July 14th. Today the Sun will be up for 15 hours and 16 minutes, setting at 9:26, and it will rise tomorrow at 6:11. The Moon, 3 days before new, will rise at 3:46 tomorrow morning.

The most important star in the night sky, especially if you are lost, is Polaris, also called the North Star or Pole Star. Face Polaris and North is in front of you, East is to the right, west to the left and south will be behind you. To find Polaris, first find the Big Dipper. In the evening. This time of year, it’s hanging by its handle in the northwest, the direction that the sun set at. The two stars at the front of the bowl point to Polaris, which is to the right of it, now. Throughout the night, as the Earth rotates. Polaris will hold its position as all the other stars go around it in a counterclockwise direction. Polaris is at the end of the handle of the Little Dipper. That handle start’s vertically but curves to the left and is made of faint stars.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.

Addendum

A chart from Stellarium showing the Big and Little Dippers, and how the stars at the front of the bowl of the Big Dipper point to Polaris. The lines show asterisms, which are informal constellations. The blue radial grid is the Earth’s longitude and latitude lines projected on the imaginary celestial sphere. The latitude lines on the celestial sphere are called declination lines, and are 10 degrees apart. The lines analogous to longitude are called right ascension lines and are 15 degrees apart to match one hour in Earth’s sidereal rotation. Polaris is nearly at the north pole of the celestial sphere, so as the Earth rotates, it remains nearly stationary. The altitude of Polaris here is nearly 45 degrees, which approximates the latitude of my location of about 44 2/3 degrees north. Created using Stellarium and LibreOffice Draw for the captions.
Categories: Concepts, Ephemeris Program, Observing Tags: , , , ,