Astro Lab Midterm

Page 1

WEEK/LAB 1- locate and identify planets, stars and constellations.

Heavenly objects appear to rise in the East and set in the West.

The Meridian is an imaginary line that runs from due South to due North.

An object reaches its highest point in the sky when it is on the meridian.

We will assume that the sun crosses the meridian at noon.

When an object is on the meridian it is halfway between rising and setting, and has reached its highest point above the horizon for that day.

To calculate what time an object crosses the meridian, do the following:

Use the rising and setting times to figure out how long the object is visible that day.

Take half of that amount.

Add it to the rise time of the object to get the time it crosses the meridian

stellurium-web.org

The Ecliptic

Due to the orbit of Earth around the Sun, an observer on Earth will see the Sun move relative to the background stars over the course of a year. The ecliptic is the apparent path that the Sun take relative to the background stars over the course of a year.

The Sun is always located on the Ecliptic.

The Moon and Planets are located near the Ecliptic.

The Zodiac consists of the constellations along the ecliptic.

Use the triangle shaped icon at the bottom of the simulation window to turn on the constellations.

Page 2

WEEK/LAB 2- Daily, monthly, and annual motions.

Solar vs Sidereal

Solar day- The time between two successive passes across the meridian by the sun. The mean solar day is about 24 hours, but varies based on the position of the earth in its orbit relative to the sun. The length of mean solar day is increasing due to the tidal acceleration of the moon by the earth and corresponding deceleration of the earth's rotation. About 4 minutes longer than the sidereal day. After the earth has revolved around the sun, it needs to rotate a further 1 degree to bring the sun back in line.

Sidereal day is 23 hours 56 minutes based on a distant star