Happy Beltane!

Happy Beltane! That would have been the traditional greeting in Ireland and Scotland centuries ago. Beltane, or May 1, is a cross-quarter day, or a day that is about halfway between the spring equinox and the summer solstice.

In many of those cultures it was observed as the start of the summer season and was observed by lighting large bonfires on hilltops around the countryside.

If you haven't already noticed from the changes of outside temperatures during the day, you would certainly notice a change of season by looking at the sky.

The winter constellations -- Orion, Taurus, Auriga, and Gemini -- are leaving the evening sky being replaced by the stars of the Summer Triangle -- Vega, Altair, and Deneb -- rising in the east in the late to mid-evening.

While we weren't looking, sunrise from the first day of spring until May 1, has moved about two hours later in the day, and the length of the day has increased by about an hour and 42 minutes.

That is sort of good news and bad news for the astronomer.

The temperatures are warmer for outside viewing in the evening, but the total hours of darkness for observing are growing shorter.

So, we are toward the end of our viewing opportunities for the year to see the Pleiades and Hyades star clusters which are currently low on the western horizon after sunset.

The Pleiades are the well-known Seven Sisters (if you have good viewing conditions and good eyesight) located just to the right of the giant "V" of Taurus, the Bull.

Binoculars work best for he Pleiades. Then swing back to the left at look at Taurus again. The Hyades cluster is behind and all around that "V" which marks the face -- or horns if you prefer -- of Taurus.

Aldebaran, the brightest star in Taurus, is right in the middle of the cluster, but is not part of it. Aldebaran is located about halfway to the cluster's distant location some 153 light-years away. Aldebaran is often referred to as the "Eye of Taurus."

On the evening of May Day the very nice slender crescent of a three-day old moon will be hanging just above Aldebaran. If you have a dark-sky location, look for Earthshine on the unlit portion of the lunar face.

Our "Parade of Planets" is still going on in the early evening hours. Look in the southwest about an hour after local sunset for very bright Jupiter. Now look to the east, at about the same height above the horizon for the bright red spot that is Mars. Down low, near the western horizon is the ringed planet Saturn. Saturn will be best observed in a telescope.

In the early morning hours at about 6 a.m. MDT look above the eastern horizon for the very bright Venus. Toward the end of the month the fading moon will help us locate the outer giant planets Neptune and Uranus as well as make a very close pass by Venus.

SKYWATCH: First quarter moon, May 6.

NEXT WEEK: On May 3 and 4 the moon will pass by Jupiter in the early evening hours.

If you are out looking, swing your view to the east to try and catch very bright Vega, the brightest star in Lyra, the Harp. It is the first of the three stars of the Summer Triangle to make an appearance.