Author: Richard Beare, Jessica Barton

Introduction:

This is a straightforward project to image a number of planetary nebulae in color. Despite the name, a planetary nebula has nothing to do with planets. It is the shell of brightly glowing gas that is left, expanding out into space, when an average sized star runs out of nuclear fuel and loses its outer layers. Many planetary nebulae are extremely beautiful objects.

Planning

• Book an observing slot, preferably when the Moon is not visible.

• Once you know when you will be observing, you will need to choose a number of nebulae to observe that will generally be higher than 30 degrees. To plan your session in advance, you can use sky charts or planetarium software. In a half-hour session you should be able to obtain about 5 images once you’ve taken slewing (moving the telescope) and exposure times into account.

• You can select nebulae of a variety of different types, e.g. planetary, diffuse and reflection.

• Background Information – You can read about different types of nebulae before your session.

Observing

Use the telescope to get color images of each nebula you chose to observe. Use an exposure time of 180 seconds. When your observing session is over, you will able to save your images to your computer. They will be zipped and in .fits format so you will need special software to open them.

Analysis

• If you wish, you can print the images out using the best print quality available to you. But do not worry if you cannot print the images out.

• Look at each nebula carefully, looking at the overall shape, the colors and any other features you can see. For example some nebulae have several shells of glowing gas (M57 right), while others have structures that look like fingers inside them (M16 below).

• Describe your observations in your own words.

Evaluation

Think about the following questions:

• What factors might have limited the quality of the images you obtained, for example poor atmospheric seeing conditions, bright moonlight, twilight?

• Are there any ways that you would improve on what you have done if you were to do theproject again using the same targets?For example, would you use different exposure times or different filters?

• Can you think how you might learn more about the planetary nebulae you have imaged by using different filters (broadband and narrow band)?