*** Almanac for the currently specified date ***:
Almanac for Roque de los Muchachos:
long.   1 11 31 (h.m.s) W, lat.  28 45.5 (d.m), elev.  2326 m
pseudo-Greenwich Daylight Savings Time assumed from 2 AM on
1997 Mar 30 to 2 AM on 1997 Sep 28; standard zone =   0 hrs W

For the night of: Sat, 1997 May 17 ---> Sun, 1997 May 18
Local midnight = 1997 May 17, 23 hr UT, or JD 2450586.458
Local Mean Sidereal Time at midnight =  13 31 11.2

Sunset ( 2326 m horizon):   21 04 GDT; Sunrise:    7 11 GDT
Evening twilight:   22 26 GDT;  LMST at evening twilight:   11 57
Morning twilight:    5 49 GDT;  LMST at morning twilight:   19 21
12-degr twilight:  21 54 GDT -->   6 22 GDT; night center:    2 08 GDT

Moonset :    5 00 GDT   
Moon at civil midnight: illuminated fraction 0.809
4.4 days until full moon, RA and dec:  12 19 35,  -1 53.5

The sun is down for 10.1 hr;  7.4 hr from eve->morn 18 deg twilight.
 0.8 dark hours after moonset and before beginning of twilight.