Scales of Measurement

3 10 6 arcseconds Angular size of a 10 M Schwarzschild black hole in M31 0:0002 arcseconds Typical VLBA resolution at 43 GHz 0:0005 arcseconds Person on the Moon 0:001 arcseconds Typical VLBI resolution 0:001 arcseconds Typical gravitational microlensing image angular separation 0:0015 arcseconds Hipparcos satellite astrometric positional accuracy 0:04 arcseconds Hubble Space Telescope FOC optical angular resolution 0:1 arcseconds VLA largest con guration resolution at 23 GHz 0:1 arcseconds Hubble Space Telescope WFC optical angular resolution 0:15 arcseconds 1 meter optical re ector yellow light di raction limit 0:5 arcseconds WHT MARTINI guide star system resolution 0:6 arcseconds Rough optical telescope atmospheric seeing limit 0:8 arcseconds Angular diameter of Europa 1 arcseconds AXAF X-ray satellite angular resolution goal 1:32 arcseconds Yearly proper motion of Sirius 1:75 arcseconds Gravitational de ection of a light ray which grazes the Sun 2:9 arcseconds Angular diameter of a M31 sized galaxy at z = 0:5 in optical light 5 arcseconds ROSAT X-ray satellite HRI angular resolution 8 arcseconds Angular separation of the gravitationally lensed quasar 0957+561 25 arcseconds ROSAT X-ray satellite PSPC angular resolution 36 arcseconds Angular diameter of Jupiter 120 arcseconds Human eye resolution 120 arcseconds Typical optical telescope eld of view 150 arcseconds Rough Crab Nebula radius 210 arcseconds Rough Cir X-1 radio nebula radius 400 arcseconds Cluster imprint on the cosmic microwave background radiation 480 arcseconds OVRO 5.5 meter 32 GHz telescope resolution 700 arcseconds Jodrell bank 250 foot 1 420:4 MHz telescope resolution 1 200 arcseconds ROSAT X-ray satellite HRI eld of view radius 1 500 arcseconds ASCA X-ray satellite GIS eld of view radius 1 865 arcseconds Angular diameter of the Moon at its mean distance 1 800 arcseconds 100 Mpc structure imprint on the cosmic microwave background radiation 1 922 arcseconds Angular diameter of the Sun at its mean distance 2 700 arcseconds Largest dimension of W50 (ARAA 22, 524) 3 100 arcseconds Maximum angular scale of causal connection on the cosmic microwave background radiation 3 600 arcseconds ROSAT X-ray satellite PSPC eld of view radius 10 800 arcseconds Angular diameter of the LMC 14 400 arcseconds Angular diameter of M31 in optical light 19 800 arcseconds Palomar Optical Sky Survey plate eld of view 25 200 arcseconds COBE DMR resolution limit