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  • Rapt in Awe

    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Events for April 2010: Venus, Mercury, the Moon, Mars and the Bees, Algol and some morning meteors

The “events” post assumes a new, chronological format this month. The idea is two-fold:

  1. Make it easy to mark your calendars for events worth making special plans to see.
  2. Give you a place to check before going out to observe to see if anything special is happening that night.

There is one category of special events worth checking on, however, that we don’t list here because they’re very specific to where you live and when you observe. These are events involving man-made objects in space – the passages of the International Space Station, Iridium flares, and other bright satellite and space craft passages. There are two excellent ONLINE sources for such events. I urge you to check both, see how they differ, and then make your own decision as to what works best for you.

  • The first is provided by Spaceweather, and you’ll find it by going to their Web site and clicking on the “Satellite Flybys” link on the right, or  by going directly here.
  • The second is the Heavens Above site, and while this requires you to register, the process is painless and free and the result is a lot of information that is specific to your location. You need to know your latitude and longitude, but you can get them by using the link in the “configuration” section near the top of the Heavens Above page. This is a one-time process. Once registered and logged in, study the menu – there’s a wealth of information on satellites and many other things.

April 2010 Astronomical events

Note: While many events are visible throughout the world, the exact time and location in the sky can be dependent upon your latitude and longitude. Since I’m in the mid-northern latitudes (41.5N, 71.1W), specifics, where place-dependent, are calculated for this location.

April 1-15 – Mercury makes what Sky and Telescope calls its “best evening display” of the year, and brilliant Venus will point the way to it. Mercury is brightest at the start of the month and fades significantly by the 15th. But at no time can it hold a candle to Venus, which will be easily found at magnitude -3.9. Just look about a fist or two above the horizon and a tad south of where the Sun set an hour before.

While Mercury is visible to the naked eye and was well-known to ancient observers, it is easiest to find if you use binoculars to pick it out of the twilight. Start half an hour after sunset and locate Venus. In the first few days Mercury will be in the same binocular field with its brighter companion. Here is what the scene should look like on April 1 – no fooling!

From Starry Nights Pro screen shot.

This close relationship holds throughout the 15-day period, though after the first week Mercury starts dropping off towards the north, and by the 13th it may no longer be in the same binocular field – depends on the binoculars used. The 15th is special, though, for Mercury then has a close encounter with a very young Moon. (Scroll down to the listing for the 15th for details.)

April 3 – A very bright, 19-day-old gibbous moon brushes by the bright, red guidepost star Antares at dawn. For me the best time to see this event will be, I believe, between 5:15 and 5:30 am EDT. I’ll be watching in binoculars. The moon will be getting closer and closer, but dawn will be breaking and starting to wash things out. If you live farther west, you’ll see an even closer encounter. Here the separation will be almost a full degree. That is, when viewed with dark skies they will still appear separated by a space greater than the width of the moon itself. The closest approach – about an hour after sunrise for this location – will still leave a gap just about the apparent diameter of the moon itself. I like these close encounters as a reminder of the motion of the moon, which goes counter to the spin of the Earth.

April 14 – The most convenient minima of Algol, the “Demon Star” occurs this month on April 14th at 9:40 pm. Should be fun to check on it about an hour after sunset, then again around 9:40 pm. The only problem – it’s getting very low in the northwest. At 9:40 it will be just 14 degrees above the horizon and will set in a couple of hours – hardly ideal conditions, so I expect this will be the last time I’ll check on it until next fall. For more details on Algol and its eclipses, see the post here.

April 15 – The Venus and Mercury show goes out with a bang, as a 1.4-day-old crescent moon joins them about one fist above the horizon 30 minutes after sunset to the west northwest. Again, Venus should be easy to pick out with the naked eye. Once you have it, use your binoculars and get it in view with them, then move down and to the right just a bit and you should encounter Mercury and the crescent moon. The exact age of the moon and closeness of this encounter will depend on your longitude. From where I sit (41.5 degrees N latitude and 71.1W longitude), the Moon will be just 1.4 days old and less than a degree away from Mercury, which will have dimmed to magnitude 1.5. I don’t expect this to be easy to see. But it all can be visible to the naked eye given an unobstructed western horizon and very clear skies. Once you’ve located it with binoculars, you probably will be able to see it with the naked eye. All depends on a modicum of skill and a lot of luck 😉

Here’s what it should look like.

From Starry Nights Pro screen shot.

April 16-18Mars and the Beehive (M44) mix it up in a delightful pairing for binocular users. Mars has begun its eastward movement against the background stars, and in doing so rolls right between the Beehive cluster and Asellus Borealis, the “Northern Ass.” Actually, this will make a nice binocular grouping from about April 11 to the 23rd, so if the weather doesn’t cooperate on the best nights, try one of the alternatives. I love it when planets get near distinctive stars and star groups because it’s easier then to chart their motions from night to night. So I would urge you to look at Mars with your binoculars at least two nights during this time frame and use the chart below to mark its position. (For other charts to help you locate Mars and the Beehive, see this posting. )

Click image for larger version. Prepared from Starry Nights Pro screen shot.

Download a printer-friendly version of this chart here.

April 22-23 – Greet the dawn with some meteors! Sky and Telescope says these are are the best dates for the Lyrid meteor shower this year. But with the moon offering interference this is a pre-dawn event and the Lyrids seldom put on a big show. If it’s clear, my plans are to be out about 2:30 am. By then the just-past first quarter moon will have set, so it won’t offer interference, and I’ll have a couple of hours before the pre-dawn light begins to wash out the eastern sky. The next night, the Moon will be a bit brighter and sets about 45 minutes later, so there won’t be as much dark-sky observing time available. I like to be aware of this kind of event, but I don’t plan my observing around it. I go out to observe other things and pause once in a while to sit back, look up at the sky for several minutes, and hope I get lucky. Hey – if it’s clear and I can do that, I’m already lucky! 😉

April 24, 25 – Venus and the Pleiades have a relatively close encounter making a nice binoculars view. Actually, they should both fit in the same low-power binocular field from about April 20 to the 28th, but it’s on the 24 and 25 that Venus is closest as it scoots past. The Pleiades are getting closer to the western horizon with each night. Venus is moving in the opposite direction, higher in the sky each night. (It will be our western evening star right into September.) By the 28th it’s about halfway between the Pleiades and the Hyades, though the clusters are getting so low they’re losing much of their luster. Getting back to the 24th and 25th, Venus will be simple to spot. Look for it about an hour after sunset and about one fist above the horizon to the west northwest. Then look for the Pleiades to the northwest of Venus in the same binocular field. Sweeping a little to the southeast of Venus (up and to the left) with your binoculars you should pick up the Hyades and Aldebaran, but not in the same binocular field as Venus.


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