sky with 05 mag limit
sky with 15 mag limit
sky with 25 mag limit
sky with 35 mag limit
sky with 45 mag limit
sky with 55 mag limit
sky with 65 mag limit
sky with 75 mag limit
Maps for GLOBE at Night at latitude 0°, Mar 17, 21 h local time (Sun is at -43°). Fixed stars would be in the same position on Jan 17, 1 h; Feb 1, 0 h; Feb 15, 23 h; Mar 2, 22 h; Apr 1, 20 h (i.e., on local sidereal time 8:43). Orion's belt is 88° to the right from S, at 43° height. The brightest star is Sirius. Lines from North (or East, South, West) to zenith shown with crosses each 10°. Map vertical size 50°. Jan Hollan, CzechGlobe and www.astro.cz/darksky.

The maps are computed for clear-sky atmospheric extinction of starlight amounting to 0.25 mag in zenith, which corresponds to a rather transparent air. The limits given in the bottom right corner (the unit is omitted, it is called magnitude with a symbol mag) concern true amounts of light coming to the face of the observer from any of the faintest stars plotted. The scale is a queer astronomical one, when 0 mag corresponds to 2.5 µlm/m2, 1 mag to 1 µlm/m2 (microlumen per square metre) and 5 mag to o 2.5 nlm/m2 (nanolumens per square metre). Unpolluted sky enables that even stars illuminating your eyes by not more than 0.2 nlm/m2 may be seen. The real visibility of stars is limited by the actual luminance of the sky, which may be much increased over the natural value of 1/4 mcd/m2 due to artificial lighting. On extremely light-polluted sky, just some brightest stars may be visible, appearing faint to the eyes not adapted to the true darkness.