Perhaps you should try some spelling variations:
practical astronomy » nautical astronomy, positional astronomy
optical astronomy » nautical astronomy, spherical astronomy, positional astronomy
astronomy sergey » astronomy survey, astronomy surveys, astronomy seven
more positional » more positioning, aware positional, more conditional
pure positional » aware positional, pure conditional, pure rotational
moore optical » moire optical, more optical, core optical
patrick more » patrick moyes, patrick mark, patrick marx
patrick mkie » patrick mackie, patrick mein, patrick m

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