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What can you see with a Telescope??

Posted by Steve Mallia on 10/9/2014
Have you ever wondered what you could see with your telescope?

Things you can see with a telescope based on its aperture

60-70 mm refractors, 70-80 mm reflectors:

  • binary stars with angular separation of over 2", e.g. Albireo, Mizar, etc.;
  • faint stars (up to 11.5 stellar magnitude);
  • sunspots (with an aperture filter);
  • phases of Venus;
  • lunar craters (8 km in diameter);
  • polar ice caps and maria on Mars during oppositions;
  • atmospheric bands on Jupiter and the Great Red Spot (GRS) under ideal conditions, four moons of Jupiter;
  • rings of Saturn, Cassini Division under ideal conditions, pink atmospheric band on the planetary disk;
  • Uranus and Neptune as stars;
  • large globular, e.g. M13, and open clusters;
  • almost all of the Messier objects (not detailed).

80-90 mm refractors, 100-120 mm reflectors, 90-125 mm catadioptric telescopes:

  • binary stars with angular separation of over 1.5", faint stars (up to 12 stellar magnitude);
  • structure of sunspots, granulation and solar flares (with an aperture filter);
  • phases of Mercury;
  • lunar craters (5 km in diameter);
  • polar ice caps and maria on Mars during oppositions;
  • clearer view of atmospheric bands on Jupiter and the GRS, shadows cast by moons onto the planetary disk;
  • Cassini Division in the rings of Saturn and 4-5 moons;
  • Uranus and Neptune as small disks with no details;
  • tens of globular clusters, bright globular clusters are resolved into cosmic dust at the edges;
  • tens of planetary and diffuse nebulae and all Messier objects;
  • brightest objects from NGC;
  • some details are resolved on the brightest and largest objects;
  • details are not resolved during observations of most galaxies.

100-130 mm refractors, 130-150 mm reflectors and catadioptric telescopes:

  • binary stars with angular separation of over 1", faint stars (up to 13 stellar magnitude);
  • details of lunar highlands and craters (3-4 km in diameter);
  • spots in the atmosphere of Venus may be seen with a blue filter;
  • numerous details on the surface of Mars during oppositions;
  • features in the atmospheric bands of Jupiter;
  • atmospheric bands on Saturn;
  • plethora of faint asteroids and comets;
  • hundreds of clusters, nebulae and galaxies;
  • spiral features of the brightest galaxies (M33, M51);
  • a large number of objects from NGC (features may be observed on most objects).

150-180 mm refractors, 175-200 mm reflectors and catadioptric telescopes:

  • binary stars with angular separation of less than 1", faint stars (up to 14 stellar magnitude);
  • lunar features (2 km in diameter);
  • Clouds and dust storms on Mars;
  • 6-7 moons of Saturn, planetary disk of Titan may be observed;
  • Spokes in the B ring of Saturn, at the peak of visibility;
  • Galilean moons as small disks;
  • at such apertures, resolution is more dependent on viewing conditions, rather than practical power;
  • some globular clusters are resolved into individual stars;
  • with minimal light pollution most features of a number of galaxies and nebulae may be observed.

200 mm refractors, 250 mm reflectors and catadioptric telescopes (and beyond):

  • binary stars with angular separation of 0.5" (under ideal conditions), faint stars (up to 15 stellar magnitude);
  • lunar features (less than 1.5 km in diameter);
  • small clouds and features on the surface of Mars, at times Phobos and Deimos may be observed;
  • a large number of features in the atmosphere of Jupiter;
  • Encke Gap in the rings of Saturn, planetary disk of Titan;
  • Triton, moon of Neptune;
  • Pluto as a faint star;
  • viewing conditions have a great effect on the quality of produced images;
  • thousands of galaxies, star clusters and nebulae;
  • almost all of the NGC objects, faint colors may be observed in the brightest nebulae;
  • finer details on many NGC objects.