Skywatch Line for Friday, March 25, through Sunday, March 27, 2016

This is Dudley Observatory’s Skywatch Line for Friday, March 25, through Sunday, March 27, 2016, written by Alan French.

Reaching full this past Wednesday, the Moon is moving toward last quarter, so a waning gibbous Moon rises in the late evening. Moonrise is at 9:25 PM Friday, 10:22 PM Saturday, and 11:18 PM Sunday.

The Sun now sets around 7:15 PM and the last vestiges of twilight are gone just before 9:00 PM, so there will be a short window of dark moonless skies Friday, with increasingly long windows on the following nights.

With the improving weather it’s a good time to learn the constellations or expand your knowledge. It’s fun to know your way around the night sky and comes in handy when a new comet makes an appearance. Some comets are bright and obvious, so they’re easy to find. But many are only faintly visible to the unaided eye or only visible with binoculars. Without a frame of reference these can be hard to spot. Everyone wanted to see Halley’s Comet back in 1986. It was visible by eye for a while, but you needed to know where to look, and there was a longer period when binoculars were required to spot it. For people unfamiliar with the sky, it was almost impossible to find.

The simplest gadget for learning the constellations is a planisphere. A disk with the stars and constellations visible from our latitude rotates within a window and can be set for any time on any night of the year. Planispheres do not know Daylight Saving Time, so set if for an hour earlier than the current time. Use a dim red light to view the planisphere – this preserves your eye’s night vision.(You can simply put red plastic or construction paper over a regular flashlight.)

Today, most people use a planetarium app on their phone, tablet, or other electronic device. These are very handy and easy to use, but they have one drawback – they are often too bright to preserve your night vision, even when set on “night mode.” Many do have a strong advantage – you can point your device at the sky and it will show and identify what you’re looking at. Handy, but it’s still useful, fun, and rewarding to know your way around the sky without such help.

Spending time enjoying the night sky has other benefits. I often hear the unmistakable “Who cooks for you? Who cooks for you-all?” call of the Barred Owl. On some nights a Great Horned Owl, with his deep, muffled rhythmic “ho hoo hoohoododo hooooo hoo.” On rare occasions the chilling descending whinny of an Eastern Screech Owl breaks the quiet of the night.

The verbal descriptions of owl vocalizations are often adequate, especially for the Barred Owl, one of our most common owls, but today you can find audio recordings on the web, nicely allowing you to learn “Who’s” around at night. You can start with the Great Horned Owl here, and then “Search” the site for the other owls.

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