Perhaps you should try some spelling variations:
"amateur astronomical" » "amateur astronomers", "amateur astronomer's", "other astronomical"
"amateur astronomy" » "amateur astronomers"
"amateur astronomer" » "amateur astronomers", "amateur astronomie"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("amateur astronomer") OR ((("amateur astronomical") OR ("amateur astronomy")))).
• Removing quotes may allow a broader search: (( amateur astronomer ) or ((( amateur astronomical ) or ( amateur astronomy )))).
• Adding a wildcard symbol may retrieve word variants: (("amateur astronomer") or ((("amateur astronomical") or ("amateur astronomy"))))*.