Is this page a copy?
Since there are now many copies of my astronomy material scattered over
the web, it is easy to come across an old version of a web page that may have
an error in it or missing material. So you will need to verify that you
have the updated version.
If your web browser's URL does not have
http://www.astronomynotes.com/ or https://www.astronomynotes.com
at the beginning of the astronomy material you are reading, the page was
copied from Nick Strobel's Astronomy Notes
web site. He does not take responsibility for any errors and incomplete
material in copies or mirrors of any part of his web site.
Use your browser's ``Back'' button to go back to the astronomy material you
were reading or select the following link to go to the official Astronomy Notes web
site.
Author: Nick Strobel