Perhaps you should try some spelling variations:
practical astronomy » positional astronomy
optical astronomy » spherical astronomy, positional astronomy
astronomy sergey » astronomy survey, astronomy surveys, astronomy seven
moore nautical » board nautical, mile nautical, moore national
patrick moocs » patrick mons, patrick moyes, patrick moore's

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: (( the patrick moocs ((practical astronomy) OR (optical astronomy)) sergey ) OR ( the patrick moore nautical astronomy sergey )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( the patrick moocs ((practical astronomy) OR (optical astronomy)) sergey ) or ( the patrick moore nautical astronomy sergey ))".
• Adding a wildcard symbol may retrieve word variants: (( the patrick moocs ((practical astronomy) OR (optical astronomy)) sergey ) or ( the patrick moore nautical astronomy sergey ))*.