{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Coordinates on the Celestial Sphere

Coordinates on the Celestial Sphere - and the sky segment...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Coordinates on the Celestial Sphere The right ascension (R.A.) and declination (dec) of an object on the celestial sphere specify its position uniquely, just as the latitude and longitude of an object on the Earth's surface define a unique location. Thus, for example, the star Sirius has celestial coordinates 6 hr 45 min R.A. and -16 degrees 43 minutes declination, as illustrated in the following figure. Right Ascension and Declination for Sirius This tells us that when the vernal equinox is on our celestial meridian, it will be 6 hours and 45 minutes before Sirius crosses our celestial meridian, and also that Sirius is a little more than 16 degrees South of the Celestial Equator. Keeping your Perspective Do not become confused because the perspectives in the celestial sphere diagram
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: and the sky segment diagram containing Sirius are different. In the celestial sphere diagram one is imagining an outside view of the celestial sphere (from a vantage point beyond the most distant stars that we see with the naked eye). In the diagram showing the position of Sirius in the sky the view is instead the actual sky as viewed from the Earth (that is, from the center of the sphere in the first diagram). Thus, the directions get reversed: moving to the right from the vernal equinox in the first diagram will look like moving to the left as viewed from its center, which is the perspective of the second diagram (that is, the actual view of the sky from Earth). That direction, by convention, is chosen to be the positive direction for right ascension....
View Full Document

{[ snackBarMessage ]}