Article as first published in The Shetland Times March 2001, formatted by astronomy.shetland
The Spring equinox
occurs on the 20th March. The Sun moves North above the celestial equator. The length of daylight becomes longer than night.
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Day |
Sunrise |
Sunset |
Moonrise |
Moonset |
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1 |
7:04am |
5:33pm |
09:04am |
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15 |
6:22am |
6:08pm |
12:59am |
08:34am |
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30 |
5:37am |
6:44pm |
07:46am |
12:31am |
The Moon is full on the 9th and is new on the 25th.
Planets
Mercury
is close to the Sun this month and difficult to see.Venus
is moving closer to the Sun. It shines brilliantly just aftersunset but is now closer to the horizon.
Mars
is a morning object, low in the south at about 6am at thebeginning of the month and in the south at 5am by the end of the
month. On the morning of the 15th the Moon will be just above Mars.
Jupiter
and Saturn are in the constellation of Taurus - Jupiter is onthe left and Saturn on the right. They are moving closer to the Sun
and can now be seen in the south-west after the Sun sets. If you want
to get some good views of these planets or photograph them along with
the Pleiades then this month is the time to do so.
Uranus
and Neptune are close to the Sun this month but moving furtheraway from it and Pluto is a morning object for medium to large telescopes.
As the night
passes the stars appear to move across the sky. Theyrise in the east and set in the west. This is really an illusion as it is the Earth which is moving, not the stars. The Earth spins on its axis from west to east and the stars appear to spin across the sky about the same axis but in the opposite direction. This means
that the stars at the celestial equator - the projection of the Earths equator on to the sky - move the quickest. While the stars at the North Celestial Pole - where the North Pole is projected on to the sky - move the least.
By chance there is a star very near the North Celestial Pole - Polaris, known as the Pole Star. Its not the brightest of stars but is easy to find. Using the constellation of the Plough, which is easy to find, the two pointer stars can be used to lead to Polaris. Find the stars Merak and Dubhe in the Plough. Imagine a line from Merak through Dubhe. Continue this imaginary line for about six times the distance between the two stars. You arrive at Polaris.
If you stand long enough or take a long exposure photograph you will see that some stars do not set but just move around Polaris. these tars are circumpolar.
If you were able to nip up to the North Pole and look straight up there would be Polaris. However, at a latitude of 60 degrees North, in Shetland, Polaris is at 60 degrees altitude in the sky. So if you are really lost you can work out where North is and your latitude all from one star.
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