Cumberland Times-News

June 2, 2012

Get ready, watch the transit of Venus safely

Bob Doyle, Columnist
Cumberland Times-News

— Tonight’s and tomorrow’s evening moons will be very full. (Actual time when the moon is directly opposite the sun is 7:11 a.m. tomorrow, the exact time of full moon.)

On both evenings, the moon will quite bright as our companion will be near the part of its orbit where it is closest to Earth. Tonight the moon will appear in the Scorpion while tomorrow night, the moon will have moved into the Serpent Bearer (Ophiuchus).

This group is the 13th constellation along the moon’s and sun’s sky path. The moon is now in the most southerly part of the zodiac, cresting only about 1/3 of the way up in the South in the early morning hours.

The event that many sky gazers have been anticipating is this Tuesday’s Transit of Venus across the sun’s disk, starting just after 6 pm.

To safely see this event, you need No. 2414 welders glasses or you can view the projected image of the sun with a telescope on a white screen.

To aim a telescope at the sun, just look at the shadow of the telescope’s tube on the ground. When the shadow of the tube gets as round as it can be, the telescope is aimed at the sun. If you have a low powered eyepiece in place, you can see the glare of the sun’s disk on the surface of the eye lens by viewing it from the side.

You must never look through the telescope at the sun, for it will quickly fry the central vision region of your retina.

Adjust the telescope so that the disk appears centered. Then bring your poster board into position so it catches the sun’s image about a foot away from the telescope. You may have to adjust the focus to get a sharp image. Then you and several people at the same time can safely the sun’s disk and the small dark dot (the planet Venus).

If it is clear, the Cumberland Astronomy Club will have several telescopes set up in the parking area behind Mountain Ridge High School in Frostburg. These telescopes will have solar filters so you can look through them safely for the sharpest detail.    

The chance of clear skies in this local area then is less than 50 percent. There will be observers in Hawaii, Midway Island, the Middle East and Australia that will have a much better chance of viewing the transit.

Transits of Venus across the face of the sun are rare because of the tilt of the Earth’s orbit to Venus’ orbit. Venus will then be 27 million miles away from the Earth. Our neighbor world will appear only 1/33th as wide as the sun itself. We had our last Venus transit in 2004 and the next one will be in 2117.

In the past, transits of Venus were used to establish the Earth sun distance by having a number of observers note the time of ingress (when Venus’ disk is first completely on the sun’s disk) and time of egress (when Venus’s disk clears the edge of the sun).

  In mid-June, we will have our earliest sunrises of the year (about 4:46 p.m. in the Tri-State area). Summer will officially begin about 7 p.m. on June 20, when the sun’s direct rays reach farthest North to latitude 23.5 degrees. Our latest sunsets will be in late June, when the sun sets about 8:46 p.m.

  In late June, the brilliant planet Venus and the bright planet Jupiter will shine in the eastern dawn with Jupiter above Venus.

  The moon will appear half full in the southern dawn sky on June 11. Then on June 17, the crescent moon will appear close to the bright planet Jupiter in the 5 a.m. dawn.

On June 19 in mid-day, the moon will swing from the morning to the evening side of the sun (New Moon). A narrow crescent moon will appear to the left of the planet Mercury on June 21 and 22 in the 9:30 p.m. western dusk.

On June 26, the evening moon will appear half full (like a tilted “D”), offering the best views of its craters and mountain ranges through binoculars. On June 27 and 28, the moon will appear near the planet Saturn.

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.