The moon will be in conjunction with the Saturn and Spica duo tonight. The view shows the sky at nightfall facing south. Created with Stellarium

Splashdown! The SpaceX Dragon cargo ship landed at departed the space station earlier this morning and landed safely in the Pacific Ocean off Baja California some 560 miles south of Los Angeles 10:42 a.m. CDT.  Once recovered by ships at sea, the capsule will be retrieved and the scientific equipment packed away by the astronauts removed. Nice to see the mission end as successfully as it began.

Tonight be sure to watch a very cool conjunction of the gibbous moon, Spica and Saturn. The three gather routinely once a month in different configurations as the moon rolls by, but this time they’ll be in a straight line one under the other around 10 p.m. CDT.

Venus in transit near the edge of the sun's disk during the June 8, 2004 transit. Photo: Bob King

An even more remarkable alignment occurs next Tuesday June 5 from mid-afternoon through sunset across the Americas when Venus crosses directly in front of the sun. This very rare event, called a transit, happens at intervals of more than 100 years.

What’s nice is that when it does, we get a pair of transits separated by a just a few years. The last one happened on June 8, 2004.

My younger daughter Maria and I at the 2004 Venus transit in Tower, Minn. Not shown are the many mosquitos that enjoyed our visit. Photo: Bob King

That June morning, it was storming like crazy in and around Duluth, Minn. My younger daughter Maria wanted to come along, so I woke her up around 3 a.m. and explained we’d have to drive north as quickly as we could to find clear skies. She got dressed without hesitation, and we were soon on our way. 80 miles later, not far from Tower, Minn., we pulled off a road just as the rising sun cleared the trees at 6. For 20 minutes we watched the little black dot of Venus, plainly visible with naked eye through a safe solar filter, creep to the sun’s edge and then disappear, not to return for another 8 years.

World map showing where and what time of day the transit is visible. For a much larger version, please click on map. Credit: Michael Zeiler, eclipse-maps.com

Here we are 8 years later and it’s transit time again. This go-around, Venus crosses the sun during afternoon hours on June 5 for the Americas. European sky watchers will see it for a short period of time after sunrise June 6 Central European Time, while the entire event will be visible across the Pacific Ocean, eastern Australia, much of China and all of Japan.

If you're able to put your binoculars on a steady mount, the projection method is a good one for viewing the transit. Photo: Bob King

Unlike a solar lunar eclipse, when the moon passes in front of the sun, the transit lasts some 6 1/2 hours because Venus is much further from Earth than the moon and appears to move much more slowly across the sky. It also has a smaller profile – only 1/30 as big as the moon.

This will be a leisurely event that can be enjoyed any which way provided you have a safe solar filter like a pair of eclipse glasses or a #14 welder’s glass.

The black drop effect is caused by a slight smearing of Venus by turbulence in the Earth's atmosphere combined with imperfect telescope optics.

At 1 arc minute in diameter, Venus will be visible as a tiny but distinct black dot against the bright sun. Binoculars, either wrapped with filters or used to project the sun’s image on a piece of white cardboard, will provide a more satisfying view. Telescope owners can thrill to watching the planet slowly enter the sun’s face. Just before Venus “separates” from the inner edge of the sun and again on its departure, watch for the black drop effect, when a black ligament appears to connect the planet to the inner limb of the sun. If the atmospheric seeing is good, observers may even see the slightly hazy appearance of Venus’ own thick atmosphere.

Venus travels from east to west across the sun next Tuesday. Times shown are Central Daylight for Duluth, Minn. and mark the planet's entry and exit points from the sun. Add an hour for Eastern, subtract one hour for Mountain and two hours for Pacific times. Illustration: Bob King

I can’t wait for Tuesday and hope you’re excited about it too. The event starts a few minutes after 6 p.m. Eastern time, 5 p.m. Central, 4 p.m. Mountain and 3 p.m. Pacific. Maximum transit, when Venus is as deep into the sun as it gets, happens around 8:25 p.m. CDT or about half an hour before sunset here in Duluth, Minn. Like the partial solar eclipse of two weeks ago, photo opportunities around sunset should be excellent.

Click HERE for a table listing the transit start, maximum and end times for a list of U.S. cities, HERE for Canadian cities and HERE for the rest of the world. Times vary by only a few minutes across the U.S. and Canada. Be aware that the times for Memphis and Minneapolis are incorrectly shown as Eastern. Subtract an hour for the correct one. Here’s another interactive time link.

I’ll have another installment on the transit in the coming days, so please stop back.