Whats Up, Ron? is a monthly almanac for Northern American astronomersastras


by Ronald A. Leeseberg, the Star Geezer

April 2011 - Vol. 15 No. 4

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Features: Calendar | Lunar Almanac | Monthly Topic

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Angular Measurement Review: It is interesting to note that the relationship between the angle subtended by combinations of fingers on your fully outstretched arm are the same for all viewers. This is due to the fact that the hand's size is proportional to the arm's length. A shorter arm is attached to a smaller hand while a longer arm is attached to a larger hand, thus the angle measured remains the same. If you hold your arm fully outstretched, your little finger, when sighted down your arm, is one degree wide. Your three middle fingers is five degrees, your fist, 10 degrees, and the distance between your little finger and your pointer finger is 15 degrees no matter what your age or size.

As springtime blooms and the days lengthen, the stars of the "winter triangle" disappear into the evening twilight. This month, the "big dipper" (Ursa Major) is high overhead at around 10 pm. If you follow the curve of the dipper's handle and continue on, you will arrive at the bright star, Arcturus (Bootes). Now continue following the same curve and you will arrive at another bright star, Spica (Virgo), in the SE. Virgo lies on the "ecliptic", the "path" that the Sun, Moon and the five bright planets travel. If you now move W along the ecliptic, you will find another bright star, Regulus (Leo), almost directly below the bowl of the big dipper. Moving further W, the twin stars (Pollux and Castor) of Gemini, glow just above the ecliptic.

You might get a peak at MERCURY if you look W just after sunset on the 1st. It reappears on the 9th., very low, in the predawn sky. You will definitely need binoculars to view! VENUS will be very bright in the predawn sky, about 4 degrees above and to the right of Mercury. It rises at about 5:30 AM. If you look W, you might also MARS at about this time. Again you will probably need binoculars. JUPITER hugs the W horizon and you just might see it because it is so bright. The only naked eye planet visible in the night sky this month is beautiful SATURN. It will be visible in the E sky as night falls. Better views follow as it ascents higher in the SE. It stands highest in the S night sky at midnight (1 AM DST). The LYRID METEOR SHOWER peaks during the night of the 22nd-23rd. Unfortunately this year's bright gibbous Moon will block the dimmer events.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time.; Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times. Unfortunately some of these events may occur during daylight hours in your area.

Look ESE at dawn to see a thin crescent Moon just above the horizon. Venus glows brightly to the far right.

Saturn is at opposition (opposite the Sun) all night. It rises around sunset and sets around sunrise. It will appear biggest and brightest this year.

About an hour after sunset, the crescent Moon shines directly above the Pleiades (M45 in Taurus) in the W sky.
At the same time, the Moon now shines to the right of the bright, reddish, star, Aldebaran. You might be able to see the Hyades (Melotte 25), an open star star cluster near Aldebaran. Best viewed with binoculars.
Use binoculars to see the open star cluster M35 (Gemini) just 2 degrees to the upper right of the Moon. This should be visible all night.
The bright star, Regulus (Leo) glows about 6 degrees above and to the left of the Moon. It should be visible all night.
Look SE about an hour after sunset to see a vertical arrangement of heavenly bodies above the full Moon. The bright star Spica (Virgo) glows above while the planet Saturn shimmers far above Spica.
The weak Lyrid Meteor Shower peaks tonight. Since the very bright gibbous Moon will blot out all but the brightest evens, wait until its radiant (Lyra, near bright Vega) is high in the sky. Observe from about 1 AM (EDT) until Moonrise. From a dark site, you may be able to see up to 10 events per hour
Look E about a half hour before sunrise to see four of the five naked eye planets as well as the Moon in one place! Jupiter is only a few degrees above the horizon. Mars is in conjunction with Jupiter (just above) while Mercury is on the curve between Mars and bright Venus. The crescent Moon shines above them all. Phases of the Moon -
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Lunar Almanac for April 2011

Phases of the Moon Phase and Date(s)

Best viewed before local midnight


Deep Space Objects

1st. Qtr

Planets & Moon



Qtr 24

Deep Space & Planets

Topic of the month: Eyepieces I (Oculars)

Your telescope's eyepiece is the most important part of its optical system. The typical eyepiece is constructed as follows:

Below are the most common eyepieces available to the sidewalk astronomer:

Unfortunately there are a bewildering number of different types of eyepieces. I would a avoid the Huygens all together. (I must confess that I own several that I use for solar astronomy. However I only use them on a small telescope with a 2.4" objective).

My main eyepieces are Orthoscopics and Plossels. I also have an RKE (Rankmodified Kellner) that seems to work as well as my Orthos or Plossils. Apparently Edmunds have solved the deficiencies associated with the older Kellner design.

As far as the Naglers and other similar eyepieces...dream stuff! Some cost more than your telescope!

--See you next month!
Ron, the star geezer

This installment of "Whats Up?" is ©2011 Ronald A. Leeseberg, encoded by Dawn Jenkins for Astra's Stargate. Images used in this installment of "Whats Up?"are of unknown origin, may be copyrighted and have been included for educational purposes only.

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