Martin Vogel Symbols
You can load the Martin Vogel Symbols with
There are several symbol sets defined. If you want the symbol for Neptune, you can either load the whole astronomic sybol set first:
\setupsymbolset [astronomic] \symbol [Neptune]
or use it as
Warning: some definitions in symb-mvs are outdated since the file symb-mvs.tex wasn't synchronized with font changes. Also, some symbol sets don't have really sensible names. The file needs to be updated.