Browsing Astronomical Objects 
Aladin sky atlas
 Astronomical Objects in General 
Constellations Galaxies Messier Objects..... Nebulae, Planetary Supernovae Others.....
 Special Objects 
Hubble Space Telescope Radio-Telescopes Reflector Refractor
 Famous Astronomical Observatories
A - Z Mt. Palomar Mauna Kea: Keck
 Astronomical Organizations
A - Z
 Astronomical Organizations International
A - Z
 Astronomical Institutes in Europe
A - Z • xxx • yyy

OK, so let's which are presented in philatelic object in a hierarchical way  
click to show infos and options...
• you can Expand all or Collapse all
• use data of the  astrothesaurus2, as defined here:
• browse by name A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
• browse by keywords A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Action ENTRY #found MEMO, Attributes and References
  Catalog Selection of Astronomical Catalogues for object displayed on stamps
  Events Astronomical Events, e.g. eclipses, transits etc.
  Observation Astronomical Observation, Telescopes, Observatories etc.
  People Astronomers, People doing astronomical Research
  Research Astronomical Research, Congresses, Institutes, Societies etc.
  Universe All Astronomical Objects grouped by spatial relationships
INFO: use  to expand by one level or  to expand all below this level

  Click here to show some info about the hierarchical basis...
• the used hierarchical structure of themes is resulting from a mainly practical approach how to classify stamps
• a more scientific approach as a general astrothesaurus can be found,at, look HERE
• a very charming approach is the classification in only 3 topics as OBSERVABLES / OBSERVERS / OBSERVATION, look HERE
• any member of a hierarchical level is member of the element(s) above (e.g. Mars is member of Planet, Planet is member of SolarSystem etc.)
•  .....