Star Viewing And Finding Constellations By Declination
Star viewing and finding constellations by declination is fairly simple.
Declination is approximate to latitude on Earth. So if your
latitude is within about 80 degrees of a constellations declination,
you should be able to see it at some point during the year.
The longitudinal angle is called the right ascension (RA for short). It measures the angle of an object east of the vernal equinox point. Since a full rotation of the sky takes 24 hours to complete, there are (360 degrees / 24 hours) 15 degrees in one hour of right ascension.
Find your latitude here(page opens in new window).
Declination is listed from zero degrees to 90 degrees North,
which is above the equator. And zero degrees to 90 degrees South
or below the equator. Northern degrees are denoted with a plus sign(+),
and Southern degrees with a minus(-).
The month listed is the month during which the constellation is
highest in the sky. Remember though that each constellation can
be visible to the sky gazing beginner during several months. Of course,
some can't be seen from certain places at all.
In the Northern hemisphere, those of us above the equator, a constellation
is visible to the star viewer for a larger part of the year as the
declination goes up.
the Little Dipper or Ursa Minor
,at a declination of +70 degrees is
visible most of the year.
In the Southern half of the planet, the opposite is true. Those constellations
with a smaller declination or larger minus number are visible longer.
Crux or the Southern Cross Constellation
with its declination of -60 degrees is visible
for a good part of the year in the Southern hemisphere.
Of course where I live at about +39 degrees N latitude it is never visible at all.
Just as the North Star Polaris, declination +89 degrees is not visible
from the Southern hemisphere.
Once you find you right ascension(RA), and declination(DEC), you can use the mini astro viewer to see the sky over your area.
A note to stargazing for beginners
Because of precession, the sun appears in constellations
at different times than the dates listed on a zodiac chart.
For example, as of 2009 the sun actually appears in the aries stars
constellation, from April 19 to May 13.
In tropical astrology which is based on a zodiac with reference points
in the tropics, the Sun appears in Aries from March 21 to April 20.
Sidereal astrology uses a system that ties the signs to the actual
constellations they represent. In sidereal astrology the sun is in
Aries from April 15 to May 15.
Ptolemy's Greek astronomy on which the classical zodiac is based
is tropical astronomy. This system defines the zodiac signs relative
to the vernal equinox regardless of actual positioning.
Return From Star Viewing to Constellations
Return From Star Viewing to 12-Zodiac-Constellations
constellations and backyard stargazing