|Mar30/||2010-12-18 17:18||-||allsky, Leo, Ori, Crux|
|Mar23/||2011-02-20 21:35||-||allsky, Leo, Ori, Crux|
|Mar2/||2011-02-20 23:48||-||Orion and around|
|HowToObserve.htm||2011-02-23 13:26||2.8K||Observation Manual|
|Feb23/||2011-09-23 21:07||-||Orion and around|
|Czech_set/||2011-03-22 19:11||-||Mapy pro Česko|
|Apr6/||2010-12-18 17:18||-||allsky, Leo, Ori, Crux|
|60all5.pdf||2011-03-16 16:22||1.1M||5 maps, 60 degrees N|
|50sall5.pdf||2011-03-16 16:24||1.1M||5 maps, 50 degrees S|
|50cz6pages.pdf||2011-03-16 22:59||1.4M||6 stran map pro Česko|
|50all5.pdf||2011-03-16 16:22||1.3M||5 maps, 50 degrees N|
|40sall5.pdf||2011-03-16 16:24||1.1M||5 maps, 40 degrees S|
|40all5.pdf||2011-03-16 16:22||1.3M||5 maps, 40 degrees N|
|30sall5.pdf||2011-03-16 16:24||1.1M||5 maps, 30 degrees S|
|30all5.pdf||2011-03-16 16:22||1.3M||5 maps, 30 degrees N|
|20sall5.pdf||2011-03-16 16:24||1.1M||5 maps, 20 degrees S|
|20all5.pdf||2011-03-16 16:22||1.4M||5 maps, 20 degrees N|
|10sall5.pdf||2011-03-16 16:22||1.3M||5 maps, 10 degrees S|
|10all5.pdf||2011-03-16 16:22||1.4M||5 maps, 10 degrees N|
|0all5.pdf||2011-03-16 16:22||1.4M||5 maps, at the equator|
I've prepared the pdf maps using my map_bsc programme in its text-only version. All are valid for 21 h local mean time.
The visibility of stars is limited by the 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. The limits given in the bottom right corner (the unit is called magnitude with a symbol mag) concern true limiting amounts of light coming to the face of the observer from individual stars, as they correspond to the level of light pollution. 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 maps are computed for atmospheric extinction (attenuation) of starlight amounting to 0.25 mag in zenith. It means that Regulus, having V = 1.35 mag outside atmosphere, appears fainter than 1.5 mag even in zenith from the Earth and is not shown in a map which has this limit. At 60° from zenith, the starlight is filtered twice that much (by ‘two airmasses’), so Regulus would appear as having 1.85 mag at such atmospheric transparency.
For extremely transparent mountain air with zenith extinction of just 0.15 mag, the number of stars would be larger in some cases, especially when they are close to the horizon.
(Actually, due to a bug in a script, maps for Leo with grey backround, png files assembled into a html, were computed for a very transparent air with extinction of starlight in zenith amounting just to 0.20 mag, which is default for the employed programme map_bsc. Another bug, missing ξ UMa for 6 mag and 7 mag Leo maps, had been corrected Mar 16, and the zenith extinction brought to the common 0.25 mag)
Listing of files used merely for producing the maps is disabled, but they are zipped in source_files.zip, together with the linux binary map_bscte and the Bright Star Catalogue in a dbase version, used for producing maps for stars brighter than 5.5 mag. Maps for fainter stars were produced using the standard hip_main.dat file. So anybody with a linux or windows machine can make similar maps ad libitum. Single maps can be made even online, using a map.php available two directories up.
As I tried to use screen maps myself (with the monitor set to minimum light possible, still 100x brigher than our city sky), the only usable mode was using a image viewer in a fullscreen mode. This way the maps with varying limits can be changed easily, without any disturbing white borders. To ease such a way of comparing the sky and the screen, I've included a series of zip files 50sallGrey.zip...60allGrey.zip for all latitudes, with the bitmaps in separate directories (a subset of the whole tree with the maps),Jenik Hollan, from CzechGlobe