One really neat thing about this system is how declination and latitude are linked

One really neat thing about this system is how declination and latitude are linked

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
One really neat thing about this system is how declination and latitude are linked. An object at your zenith (remember, that is right over your head) will have a declination value equal to your latitude! If you are located on the Earth's equator (0º latitude), at your zenith would be a declination of 0º (which is the declination of the Celestial Equator). If you are at the North pole, you are really cold, and your latitude is 90º N. If you don't freeze to death, you might notice that at your zenith is a declination of 90º N. If you are in Cedar Falls, 42.5º N latitude, then at your zenith is a declination of, you guessed it, 42.5º N. Check out Figure 4 to see this sort of arrangement. Figure 4. How declination and latitude are related. An object at your zenith has a declination value that equals the value of your latitude. Just like latitude, declination is measured in units of degrees. The two extremes are at the North and South Celestial poles: +90º to -90º respectively (or you could say 90º N and 90º S). You can't have a declination greater than +90º or less than -90º! Sometimes a degree is pretty big and you need to measure an angle that is much smaller than a degree, so you need to use a smaller unit of measure (sort of like the way an inch is a smaller unit of a foot). To make life easier, we can divide one degree into smaller units known as minutes . To be precise, 1º = 60' (the dash stands for minutes). Sometimes using minutes is not enough; even smaller units are needed. We can divide each minute up into (you guessed it) seconds . Of course, the division is 1' = 60 " (two dashes signify seconds). For those with nothing better to do, you might note that 1º = 3600". An object's declination can be given very precisely as, for example, -34º 27' 41''. A lot of times astronomers have to keep track of time (not that we ever have any dates or something like that, but just to keep track of events in the sky). If astronomers need to talk about minutes and seconds, like as in units of time, how can we know that they are talking about time units and not angle units? To distinguish between angular minutes and seconds and time minutes and seconds, the word arc second or arc minute is often used. You could say that there are 3600 seconds in a degree, or you could say that there are 3600 arc seconds in a degree. By using arc seconds people would know that you are talking about angles and not time. I should mention that angles are used for not just positions but also relative positions and
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/22/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

Page1 / 3

One really neat thing about this system is how declination and latitude are linked

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online