Astronomers now fans of summertime

Normally we outdoor types are happy to see summer arrive. The warmer temperatures, the bright sunshine, the fun outdoor activities. However, we astronomer types--we do our thing in the dark--are not so happy to see summer begin.

"But," I hear you say, "I thought you would be happy. "There are so many more and brighter objects to see in the sky, in the summer, so many more interesting objects to look at. Why would you not be happy?"

Well, you see it has to do with not so much what there is to look at, as it does how long we have to look. With the arrival of summer we have much longer days and more sunshine, conversely, that means much less dark. Longer days means shorter nights.

We always hear that the first day of summer is the longest day of the year, however, this year it is not the "only" longest day. If we want to get technical, the longest day runs from June 17 to June 26 with 15 hours and one minute of daylight on each of those days.

That means we astronomers only have--from astronomical twilight in the evening to astronomical twilight the next morning--seven hours and eight minutes of dark for observing.

Astronomical twilight is the term astronomers use to establish when good, dark-sky, viewing begins. I call it "Oh Dark-Thirty."

Just for your information, the summer solstice -- the time the Sun reaches the farthest point north it will go for the year and summer officially begins--is at 10:38 a.m. MDT on Sunday, June 21. The word "solstice" is Latin for "Sun stands still."

With 10 days of 15 hours and one minute of daylight, we can see what they mean. Of course, the Sun does not really stand still, it only seems to do that since it rises near the same point on the horizon on each of those days.

Twilight is a term used to describe the number of degrees the center of the Sun's mass is below the horizon. Civil twilight is when the Sun is six degrees below the horizon; nautical twilight is 12 degrees below; and astronomical twilight is 18 degrees below.

Astronomical twilight is when objects in the sky become visible and observation is possible. It is what we astronomers wait for to begin our observing. Unfortunately, that is about two hours after local sunset--about 10 p.m. MDT in the summer.

Astronomical twilight the next morning is just after 3 a.m. MDT, so that is slightly more than seven hours for observing.

Now, you see why we astronomers are not always thrilled with summer.

SKY WATCH: New moon, Tuesday, June 16. Get your binoculars dusted off (if you have dusty binoculars, shame on you) because Venus will take a stroll near M44, the Beehive Cluster, on Friday, June 12. Can someone say "photo opportunity" for those who are so equipped. Locating Venus will be no problem. It is the brightest thing just above the western horizon. Best time for looking is after 10 p.m. MDT. Using binoculars you will find the planet slightly right of the star cluster which is almost smack in the middle of Cancer, the Crab. If it is cloudy (or you forget), not to worry. On Saturday night it will be just above the cluster. In fact, Venus and the cluster will be in the same binocular field of view (FOV) until Thursday, June 18. This is not the first time Venus has strolled by the cluster. It did it ast in 2010. We can thank the fact that M44 is almost on the ecliptic for that. So look for Venus--and other planets, or the moon--to frequently come calling.

NEXT WEEK: Time for our moon watch again, and more astronomical blathering.