Star charts for GLOBE at Night 2020 - a preliminary edition, subject to ev. suggested corrections (at least for avoiding overlaps of labels)

Mar 20, I've added maps for the Earth Hour, Saturday March 28, 20:30 to 21:30. Search for the Zodiacal light before that time... along ecliptics toward Moon and Venus. Betelgeuse was shown in its usual brightness, but actually from November till March it was a lot dimmer, even fainter than Bellatrix. (It became bright again in April).

In April and May, I've replaced the proper name Toliman by the outspelled Greek designation of the brightest fixed star in Centaurus (concerns just maps centered on Acrux). Queer, that due to resolution of IAU, such a prominent star bears no proper name anymore, unlike its components, which cannot be seen watching the sky naturally, without a telescope – and do not need any name, IMHO.

I made no visual inspection of these charts/maps yet. Maps were produced by bash scripts, trivially edited from their 2019 versions by changing the demanded calendar dates. The 1st script to run: allsky16.sh with the updated calenadar dates, as it creates the needed directories (and makes allsky maps within them) Mmmdd, symlinked to .mm-dd ones (which exist, but are not shown by Apache). Within the directories, scripts for individual constellations and dates are then used with proper dates and old *.tex files (provided, that maps are for 21 h of local time). Then, MonDa.sh is to be used before the remaining scripts, as it creates lists of dates/latitudes to be put into the scripts instead of the old ones. all_sh.zip contains all *.tex and *.sh files used to produce the current set of maps.

Maps are for 21 h local mean time of the given date. Local time is different from the ‘civic’ time, if your longitude is different from that of the standard meridian for that time band. Being 10° westwards means your local time is 40 min lower. And during SummerTime, the local mean time is another 1 h less.

If you observe at another local sidereal times, you may use the 2019, 2018, 2017, 2016, 2015, 2014 maps, or 2012 maps (having an alternative for rather turbid air), or 2011 maps. Of course the planets were elsewhere those years, and brighter or fainter. Maps for 2011 and 2012 are for January-April only. Their pleasant feature is, they have a screen-friendly variant of white stars on a grey background. Should I add that kind of charts again?

For cases the sky luminance is very high and almost no stars are visible (as during twilight), the all-sky maps may be useful, available in subdirectories "A" or in the "latitudes" directory.

	Name	Last modified	Size	Description
	Parent Directory		-
	zipall.sh	2016-07-22 19:25	224
	zip_sh.sh	2019-11-24 11:50	329
	latitudes/	2019-11-24 10:37	-	grouped according to latitude
	latPDFsetA.sh	2019-11-23 21:55	1.2K
	latPDFset.sh	2019-11-23 21:55	1.1K
	constell/	2019-11-24 10:37	-	grouped according to map centre
	constPDFset.sh	2019-11-23 21:50	879
	constDat.sh	2019-11-23 21:51	745
	auxfiles/	2019-11-24 18:41	-
	allsky16.sh	2020-05-23 16:27	2.5K
	all_sh.zip	2020-05-23 16:27	107K
	all_dates.zip	2020-05-23 16:42	326M	date-named subdirectories together
	Sep13/	2019-11-24 09:42	-
	Oct12/	2019-11-24 09:54	-
	Nov11/	2019-11-24 09:57	-
	MonDa.sh	2019-11-23 21:05	540
	May18/	2020-05-23 13:13	-
	Mar28/	2020-03-21 16:06	-	maps for Earth Hour 2020
	Mar19/	2019-11-23 22:58	-
	Jun17/	2020-05-23 16:41	-
	Jul16/	2019-11-24 10:33	-
	Jan20/	2019-11-23 22:41	-
	Feb18/	2019-11-23 22:43	-
	Earth_Hour/	2020-03-21 16:06	-
	Dec10/	2019-11-24 10:04	-
	Aug14/	2019-11-24 09:39	-
	Apr18/	2020-04-11 08:58	-

It's a pity that thousands of millions of people are devoid of the gift of the starry sky now. There are so many terrestrial lights which are so much stronger... The world is so much light-polluted... (What pollution is that? Light from non-natural sources. See ev. Declaration for an expert attitude.)

However, even in cities we can still see some stars. From a place with no glare, like a roof high over any lamps, this is possible even in the centre of any city, provided that clouds don't prevent it. Venus, Jupiter or sometimes Mars (like in 2012 winter and spring) are bright enough to be visible even when the air is strongly illuminated from below. Comparing the maps offered at this site with the sky above you, you can get a proxy indicator how much brighter the sky is than the natural moonless one. A proxy for a quantity called luminance (luminance: how much light goes towards your eyes from a piece of the sky – this is expressed in lumens per square metre, divided by the size of that piece – expressed in steradians; the result is in lumens per square metre per steradian, or shortly candelas per square metre).

On your site, is there still a huge difference between a full-moon sky, with the air dispersing the light from the Moon, and the moonless sky with little natural luminance and perhaps a large artificial component? If yes, then you should use the moonless night to see more stars. Not everybody is so fortunate, there are sites where Moon cannot add much to the all-the-time large luminance of the heavily polluted sky. Go and explore that for yourself! Actually, such comparisons of our maps with the real sky during nights with and without Moon may become an even better proxy for the artificial component of the sky luminance. The same holds for observation during civil, nautical and astronomical twilight. In my city, Brno, there is no perceptible change after the nautical twilight ends... What's the situation at your site? Does the sky get darker during nautical or even astronomical twilight, so that more stars become visible? Start observing during civil twilight already and proceed till astronomical night. (Some more hints see at How to Observe.)

(The evening twilights: they start with the sunset, the civil one ends with Sun being at −6°, nautical at −12° and astronomical at −18°. Astronomical night is the time when the Sun is below −18°.)