That happens when you project a curved spherical surface onto a flat Both parts also illustrate the distortion The second part of the module has you do the same sort of thing using aįlat map of the sky or a globe of the celestial sphere and read off the You drag a cursor around on a flat world map or globe and read off its terrestrial System (link will appear in a new window). Terrestrial coordinates (longitude and latitude) and the equatorial coordinate Numbers involved is given at the end of this section.Ĭoordinates module of the University of Nebraska-Lincoln'sĪstronomy Education program provides a great way to make the connection between A concise summary of this coordinate system and the Polaris's position is at RA 2hr 31minĪnd dec 89 degrees 15 arc minutes. Objects half-way to the NCP are +45 degrees, objects at the NCP are +90 degrees, and Objects on the celestial equator are at 0 degrees dec, Objects north of the celestial equator and negative degrees for Measured in degrees away from the celestial equator, positive degrees for Like the latitude lines on Earth, declination (dec) is Latitude and when projected onto the sky, they become lines ofĭeclination. The lines on a map of the Earth that run east-west parallel to the equator are lines of On the sky (only if they are on the celestial equator will they be 15 degrees apart). Stars one hour of RA apart will not necessarily be 15 degrees in angular separation The lines of RA all converge at the celestial poles so two The full 360 degrees of theĮarth's rotation is broken up into 24 hours, so one hour The Sun crosses the celestial equator at the vernal equinox. Your meridian half an hour before the other. If the stars are notĬircumpolar, you will see one star rise one hour before the other.Īpart, you would see one rise half an hour before the other and cross Your meridian one hour of time before the other. Because theĪscension (RA) is measured in terms of hours, minutes, and seconds instead ofĭegrees and increases in an easterly direction.įor two stars one hour of RA apart, you will see one star cross When projected onto the sky, they become lines of right ascension. The lines on a map of the Earth that run north-south are lines of longitude and Selecting the image link will bring up a short animation of a spinning celestial You will find this system used in astronomy magazines and in The stars so, unlike the altitude-azimuth system, a star's position does notĭepend on the observer's location or time. This system is very similar to the longitude-latitude system used to specify The second way of specifying star positions is the equatorial coordinate A concise summary of this coordinate system and the numbers involved is Also, observers at different locations lookingĪt the same star at the same time will see it at a different altitude-azimuth Since stars change their position with respect to your horizon throughout the night,Īltitude-azimuth position changes. For example, a star in the southwest could have anĪzimuth between 180 degrees and 270 degrees. Starts from exactly North = 0 degrees azimuth and increases clockwise: exactly East =ĩ0 degrees, exactly South = 180 degrees, exactly West = 270 degrees, and exactly TheĪzimuth of a star is how many degrees along the horizon it is and The altitude of a star is how manyĭegrees above the horizon it is (anywhere from 0 to 90 degrees). The first is what you would probably use to point out a star to yourįriend: the altitude-azimuth system. There are a couple of popular ways of specifying the location of a celestial But probably of more importance to you is where to point your telescope orīinoculars to find that cool object talked about in the newspaper or astronomy magazine. Recently been replaced by the use of satellite systems such as the Global Positioning Was also crucial for commercial and military navigation (navigation by the stars has only To be important for determining the physical characteristics of the stars and planets. This was due in part to the influence of astrology, but later, accurate positions came See my copyright notice for fair use practices.Įarly astronomy concentrated on finding accurate positions of the stars and planets. Video lecture for this chapter This material (including images) is copyrighted!. Astronomy Without a Telescope Coordinates Chapter index in this window
0 Comments
Leave a Reply. |