Natural Calendar April 2010

Natural Calendar - April 2010

The purpose of this feature is to give scout leaders, educators and naturalists an idea of some of the natural events coming up each month. We will try to cover a variety of natural events ranging from sky events to calling periods of amphibians, bird and mammal watching tips, prominent wildflowers and anything else that comes to mind. We will also note prominent constellations appearing over the eastern horizon at mid-evening each month for our area for those who would like to learn the constellations. If you have suggestions for other types of natural information you would like to see added to this calendar, let us know!

Note: You can click on the hyperlinks to learn more about some of the featured items. To return to the Calendar, hit the "back" button on your browser, NOT the "back" button on the web page. All charts are available in a "printer friendly" mode, with black stars on a white background. Left clicking on each chart will take you to a printable black and white image. Please note that images on these pages are meant to be displayed at 100%. If your browser zooms into a higher magnification than that, the images may lose quality.

Though we link book references to nationwide sources, we encourage you to support your local book store whenever possible.

Notes and Images From March 2010

NGC 3184, March 4th, 5th and 6th, 6 inch Refractor at f12 and ST2000XCM CCD Camera, Total Exposure Time 11 Hours, 40 Minutes.

NGC 3184 is a pretty open face spiral galaxy in Ursa Major. This galaxy is a little fainter than the Messier objects in the Great Bear, and was missed by Messier in his scan of the constellation. It was not missed by William Herschel, who discovered it on March 18th, 1787, near the left hind foot of the bear. It is sometimes called the Little Pinwheel Galaxy. Distance estimates range from 25,000,000 light-years to 40,000,000 light-years.

Sky Events for April 2010:

Evening Sky:

Mercury has a fine apparition this month and should be easily visible low in the western sky after sunset. From the beginning of April to mid-month the planet should be at least 10 degrees above the horizon. The small planet reaches its greatest elongation from the Sun on April 8th. Try to find a location with a fairly flat western horizon and begin looking for the planet about 30 minutes after sunset. It will be to the lower right of brilliant Venus, which will be the first star-like object to appear after sunset. You may need binoculars to spot Mercury towards the middle of the month as it fades in brightness.

Beautiful Venus is easy to see after sunset in the western sky, and can be used to help find Mercury during the early part of the month. It will gradually climb higher in the sky after sunset as the month progresses.

Mars is high in the sky at dusk at midmonth, about 75 degrees above the horizon due south. As the distance between Mars and Earth continues to increase, the apparent diameter of Mars decreases from 9 seconds of an arc to 7 seconds of an arc. Telescopic detail on the planet will be elusive.

Look for bright Saturn about 25 degrees above the eastern horizon at dusk at the beginning of the month. The ringed planet is in Virgo. The rings are still pretty close to edge-on this month. Because of the diminished brightness of the ring system, you may be able to see fainter satellites of Saturn than you normally do with a given telescope.

Morning Sky:

The Lyrid Meteor Shower occurs in the pre-dawn hours of April 22nd and April 23rd. Although this typically is a fairly weak shower, you may want to give it a try. Best conditions will be between 1:00am and 4:00am. Look northeast towards the bright star Vega. A waxing gibbous moon will hinder observations this year.

Jupiter is just visible in the dawn sky in April, rising about an hour before the sun at the beginning of the month.

All times noted in the Sky Events are for Franklin, Tennessee and are Central Daylight Time. These times should be pretty close anywhere in the mid-state area.

Constellations: The views below show the sky looking east at 9:30pm CDT on April 15th. The first view shows the sky with the constellation outlined and names depicted. Star and planet names are in green. Constellation names are in blue. The second view shows the same scene without labels. New constellations this month in the eastern sky are Serpens Caput, the Serpent (Head), and Hercules, the Strongman. As spring progresses and Hercules rises higher in the sky, look for the globular cluster Messier 13 (M13), which appears like a small fuzzy patch of light about 1/3 of the distance from Eta to Zeta Hercules (see illustration below). A cluster of stars about 21,000 light years away, M13 can be made out with the naked eye in a dark country sky when the constellation is high in the sky. Binoculars will help pick it out.

April 15th, 9:30pm, Looking East

On Learning the Constellations:

We advise learning a few constellations each month, and then following them through the seasons. Once you associate a particular constellation coming over the eastern horizon at a certain time of year, you may start thinking about it like an old friend, looking forward to its arrival each season. The stars in the evening scene above, for instance, will always be in the same place relative to the horizon at the same time and date each April. Of course, the planets do move slowly through the constellations, but with practice you will learn to identify them from their appearance. In particular, learn the brightest stars (Like Arcturus and Spica in the above scene looking east), for they will guide you to the fainter stars. Once you can locate the more prominent constellations, you can "branch out" to other constellations around them. It may take you a little while to get a sense of scale, to translate what you see on the computer screen or what you see on the page of a book to what you see in the sky. Look for patterns, like the stars that make up the constellation Corona Borealis.

The earth's rotation causes the constellations to appear to move across the sky just as the sun and the moon appear to do. If you go outside earlier than the time shown on the charts, the constellations will be lower to the eastern horizon. If you observe later, they will have climbed higher.

As each season progresses, the earth's motion around the sun causes the constellations to appear a little farther towards the west each night for any given time of night. If you want to see where the constellations in the above figures will be on May 15th at 9:30pm CDT, you can stay up till 11:30pm CDT on the April 15th and get a preview. The westward motion of the constellations is equivalent to two hours per month.

Recommended:

Sky & Telescope's Pocket Star Atlas is beautiful, compact star atlas. It is destined to become a classic, and is a joy to use at the telescope.

A good book to learn the constellations is Patterns in the Sky, by Hewitt-White. You may also want to check out at H. A. Rey's classic, The Stars, A New Way to See Them.

For skywatching tips, an inexpensive good guide is Secrets of Stargazing, by Becky Ramotowski.

A good general reference book on astronomy is the Peterson Field Guide, A Field Guide to the Stars and Planets, by Pasachoff. The book retails for around $14.00.

Starry Night has several software programs for learning the night sky. Visit the Starry Night web site at www.starrynight.com for details.

Amphibians:

Northern Cricket Frog

Already this spring we've heard Upland Chorus Frogs, Spring Peepers, Southern Leopard Frogs, American Toads. and Cope's Gray Treefrogs. The early calls of Gray Treefrogs sound raspier than the normal trill, as if the frog needs to clear its throat. They sometimes call from small tree cavities on warm days. Listen also on warm days for Northern Cricket Frogs, American Bullfrogs, and Green Frogs. Early April is also a great time to listen for the "yeeooww" calls of Pickerel Frogs.

Birds:

The spring migration builds very quickly in April. The neo-tropical migrants are too numerous to list here, but now is the time to get out in the early morning with a pair of binoculars and welcome the new arrivals for the day. Scan the edges of ponds and creeks for Solitary and Spotted Sandpipers. Early arrivals also include Black-and-white Warbler, Black-Throated Green Warbler, Louisiana Waterthrush and Blue-gray Gnatcatcher. Listen at dusk for young Great Horned Owls and Young Barred Owls, doing their raspy "begging" calls.

Recommended:

A new guide to hawks in flight you may want to look at is Hawks From Every Angle - How to Identify Raptors in Flight, by Jerry Liguori.

The Sibley Guide to Birds, David Allen Sibley

The Sibley Guide to Birds of Eastern North America, David Allen Sibley

An inexpensive guide for beginners is the Golden Guide for Birds.

Wildflowers:

Some of our favorite Spring wildflower walks are:

The south ridge at the Owl's Hill Nature Center in Brentwood, Tennessee.

The Edwin Warner paved loop at the Warner Parks in Nashville or just about any trail in Warner Parks.

The Angel Falls trail along the Cumberland River at the Big South Fork Recreational Area, near Jamestown, Tennessee.