Position on the Earths surface

To illustrate these concepts we consider the Earth. A point on the surface of the Earth is defined by two coordinates, longitude and latitude, based on the equator and a particular meridian (half of a great circle) passing through the North and South Poles and Greenwich, England. The equator is the great circle whose poles are the North and South Poles. The longitude, X, of the point is measured east or west along the equator. Its value is the angular distance between the meridian passing...

Instantaneous phenomena

During the day a variety of phenomena may be seen. In a particular direction lies the Sun, so bright it is impossible (and dangerous) to look directly at it. In general, the sky background is blue. The Moon may also be visible, having a distinct shape though certainly not circular. If the Sun has just set or if dawn is not far away, there is sufficient daylight to see clearly. We call this condition twilight. On the horizon opposite to the twilight glow, a dark purple band is sometimes seen....

Detectors for optical telescopes

We have seen earlier that the Earth's atmosphere has a window which allows transmission of electromagnetic radiation with a range of frequencies, the centre of the band being close to the peak sensitivity of the eye. The eye is not sensitive to all of the frequencies which arrive at the bottom of the atmosphere in this band. Energy in the form of near ultraviolet and infrared radiation is arriving from space and penetrates down to ground-level but is not sensed by the eye. It can, however, be...

The reduction of positional observations I

In general, astronomical observations of an object's position undergo a process of reduction. This procedure removes known instrumental errors and other systematic effects in order to provide data about the celestial body that is as objective as possible. Such reduced observations, independent of the observer's position, are then suitable for catalogue purposes or for comparison so that changes in the body's position with time can be derived. The raw observations may be the altitude (or zenith...

Problems Chapter

Note Take the length of the sidereal year to be 365-25 days. Assume all orbits are circular and coplanar, unless otherwise stated. 1. A planet's elongation is measured as 125 . Is it an inferior or superior planet 2. The sidereal period of Mercury is 88 days. What is its synodic period 3. What is the maximum possible elongation of Venus, given that its distance from the Sun is 0-723 AU 4. The synodic period of Jupiter is 398-9 days. What is its sidereal period 5. The heliocentric distance of...