This website belongs to Richard Powell. You may copy this website in its entirety for personal use. Schools and colleges can copy this website for their own internal use. It is always acceptable to use this website for classroom projects.


All of the text on this website is my intellectual property. You are free to copy, and distribute the text, for non-commercial purposes only, and you must cite this website if you use any of the text in a derivative work. Commercial use of the text must be restricted to small quotations and should cite this website.

Maps and Diagrams

All of the maps and diagrams on this website belong to me, and are free for anyone to use under the following conditions. They are licenced under a Creative Commons Attribution-ShareAlike 2.5 Licence. This is a summary of the licence:

Creative Commons License
This work is licensed under a
Creative Commons Attribution-ShareAlike 2.5 License.

You are free:

Under the following conditions:

This licence is an acceptable Wikimedia Commons Licence.

Photographic Images

Photographs of astronomical objects on this web site are from the Digitized Sky Survey unless otherwise stated. (I have usually merged together blue and red plates to produce colour images.)

These photographs are copyrighted. Some of the pictures belong to the California Institute of Technology, and some belong jointly to the Royal Observatory Edinburgh and the Anglo-Australian Observatory.

This is the data use policy:

These data are all copyrighted material and are subject to the following restrictions on their use.

Scientists and educators who are using these data for research, teaching purposes and other non-profit activities may freely use these data and we only request that you acknowledge the source in any publication.

Commercial use of these data is prohibited without permission.

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