Caption: Sky map for the winter night sky. Click on sky_map_unlabeled_winter.pdf for the pdf file.

Features:

1. The sky map shows the middle region of the celestial sphere in Mercator projection.

2. The grid is for the equatorial coordinate system with angular coordinates right ascension (RA) and declination (Dec or δ).

3. Right ascension is the horizontal angular coordinate (gridded by vertical lines).

   Declination is the vertical angular coordinate.

4. Right ascension is given in the funny angular units hours (h), minutes (m), and secconds (s): 1 h = 15°, 1m = 1/60 h = 0.25°, 1 s = 1/60 m = 0.00625°.

   The full range of right ascension is 0h -- 24h.

   The sky map only shows the region ∼ 23.5h -- 0h -- 12.5h.

   Right ascension 0h is vernal equinox: the point where the Sun crosses the celestial equator going north on about Mar21 every year.

   Vernal equinox also means the event of the Sun crossing the vernal equinox.

5. Declination is the vertical angular coordinate (gridded by horizontal lines).

   Declination is measured north and south from the celestial equator which is zero declination.

   North is positive and south is negative.

   The sky map only extends to declination ∼ 55°, and so the north celestial pole (NCP) and south celestial pole (SCP) regions are NOT shown.

6. The curved line is the ecliptic which is the yearly path of the Sun on the celestial sphere.

   In the winter, the Sun is on the southern segment of the ecliptic (which is in the daytime sky) and the winter night sky contains the northern segment as seen in the sky map.