Mercury at Maximum Elongation

Today Mercury will be at maximum eastern elongation, as high in the evening sky as it will appear for this current apparition. After today the planet will slide back into the sunset, passing through inferior conjunction on January 14th to reappear in the dawn around the beginning of February.

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Winter is Here

Today marks the beginning of winter. While snow and ice can appear on the summit of Mauna Kea any time during the year, the most severe weather usually occurs during winter storms. We all look forward to the beautiful sight of Mauna Kea with her white coat. Of course this comes at a price, days of difficult access to the summit facilities, or no access at all. The loss of observing nights due to ice and clouds is most common from January to March.

Iced
The emergency evacuation vehicle covered with ice

Winter Solstice

Winter solstice occurs today at 18:48HST. Today the Sun will occupy the most southerly position in the sky of the year. The term solstice comes from the Latin terms Sol (the Sun) and sistere (to stand still). On this day the Sun seems to stand still as it stops moving southwards each day and begins move to the north. This is the first day of winter as marked by many cultures in the northern hemisphere. Alternately, this is the first day of summer for those folks in the southern hemisphere.

2015 Solstices and Equinoxes
  UT HST
Perihelion Jan 4 08:59UT Jan 3 22:59HST
Vernal Equinox Mar 20 22:45UT Mar 20 12:45HST
Summer Solstice Jun 21 16:38UT Jun 21 06:38HST
Apehelion Jul 6 12:59UT Jul 6 02:59HST
Autumnal Equinox Sep 23 08:20UT Sep 22 22:20HST
Winter Solstice Dec 22 04:48UT Dec 21 18:48HST
 
Source: NASA Sky Calendar