# Astronomical Exercises: Middle Level

In this Astronomy On-Line Shop you will find a variety of intriguing astronomical exercises.

These exercises are somewhat more demanding than those at the basic level. It is expected that you know some of the basic facts about astronomy before you try your skills on them. They are probable best for the 15 - 16 age group.

Just click on the titles to access the individual exercises and to try your skills!

#### II.1 Lunar Eclipse: The Moon's diameter and distance to the Earth

Use the photographs and drawings from the recent Lunar Eclipse to determine the Moon's diameter and also its distance from the Earth. Several methods are explained, some of which are quite easy.

#### II.2 How to calculate the duration of a Lunar Eclipse

Did you observe the lunar eclipse on September 27, 1996? Even if you did not, you may have thought about how astronomers calculate the circumstances of such an eclipse in advance. In this connection, an important aspect is the duration of an eclipse. Here you will learn to perform the related calculations.

#### II.3 Three motions of the Earth

Study the motion of the Earth, as it goes around the Sun. Learn about the Zodiac!

#### II.4 Mathematical Exercise related to the Solar Eclipse on October 12, 1996

Here is a detailed exercise with explanations based on observations made by Astronomy On-Line groups during the partial solar eclipse that took place on October 12, 1996.

#### II.5 Lunar Craters

Measure the size of lunar craters and learn about impact formations on the Earth and on the Moon.

#### II.6 Measuring the Earth - Moon Distance with a Laser

This exercise concerns a very basic type of measurement. You will learn about the way this is done from an observatory in France (CERGA) and be astonished how good the accuracy really is!

#### II.7 Measuring the Distances to the Galaxies by means of Cepheid variables.

,p>This exercise provides a very useful supplement to the information available in the Collaborative Project on variable stars.

However, if you think they are too simple for you, why don't you pass on to the Advanced Level?