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One Minute Venus

Posted by Eric David   10/23/2010 12:00AM

It has been 24 years since the first time I got serious with Venus and I still enjoy her company as much as I did when I first met her. The year was 1986 and I was stationed in Augsburg, Germany as part of the U.S. Army's VII Corps in Bavaria. Despite the cloudier climate than I was used to in the United States, and the high latitude (48 degrees in Augsburg), I had followed Venus for its entire evening apparition in 1986, from its emergence in the evening sky in February all the way through its conjunction with Spica very low in the west at the end of August and beginning of September.

The high latitude, combined with Venus' distance from the Sun and northerly declination, made for Venus-set around midnight in June, but by late September, the especially low angle of the ecliptic and Venus' increasingly southern ecliptic latitude made it exceedingly difficult to get a view of Venus after sunset, despite its elongation. So, based on advice in "Sky & Telescope," I tried to observe Venus during the daytime with binoculars. This sounded like a very tall order at first; how can you scan such a large patch of blank sky and hope to pick out the planet? How would I even know what to look for? In any event, sometime in September of that year I took advantage of the best weather of the year in Germany to hunt for Venus in broad daylight. Armed with 10x50 binoculars, it took some time to figure out how to estimate angular distance, the correct direction from the Sun to look at different times of the day, and to develop the technique of systematic sweeping so as to properly cover the whole area of sky in which I thought Venus should be.

The first time that I found Venus in the daylight, I was hooked! With practice, the feat became easy, and soon routine, usually with less than a minute of searching, in some cases only a few seconds from first raising binoculars to the sky to spying the small white crescent. Using trees or clouds in the sky as a means to break up the otherwise pure blue field usually helped, and the project also made me much more aware of the subtle differences in atmospheric conditions such as dust, humidity, thin clouds and pollution that can make finding Venus much more difficult. If there is any milkiness to the sky, Venus can still be found, but the reduced contrast means that if your binoculars are not in exact focus, you can easily sweep right over it. Aircraft with their contrails make convenient focusing aids to minimize this problem.

As I learned more about astronomy and sky-gazing over the years, and especially as I followed Venus through successive apparitions, I read about and then experienced each of the eight different ones from 1985 to 1993. My first year in Germany was 1985, so my first "repeat" apparition was in 1993 while living in Boulder, Colorado. Watching Venus repeat its journey through the sky from different locations, and in different life situations, has proven to be one of the truly enjoyable aspects of my astronomy experience, providing an unexpected link from one phase of my life to another. As I watch Venus in October 2010, I often think back to October 1986, in Germany, when I would go out to the parking lot during lunch and look up into the clear, deep blue sky of the Bavarian autumn and pick out Venus, shining serenely below and to the left of the Sun. I was able to follow it until about October 16 or 17, at which time it was about 15 degrees from the Sun. After that, whether for weather or other reasons, it was lost, but I was pleased to have been able to follow it for as long as I did.

Fast forward to today, and I am once again finding pleasure in picking Venus out of the blue October Virginia sky as it rounds in between the Earth and the Sun, heading for its inferior conjunction on the 29th. Being a regular reader of "Sky & Telescope" and Guy Ottewell's "Astronomical Calendar," I have read many times about how the apparition in which Venus' inferior conjunction comes at the end of October is one of the worst for northern hemisphere observers. After all, Venus passes well south of the Sun at conjunction and therefore sets before the Sun and rises after the Sun for about three weeks around that time; the time to see Venus at inferior conjunction is in March, right? Then, it passes well north of the Sun and is visible after sunset and before sunrise for several days, a feat that I most memorably accomplished in late March 2009 while doing a Messier marathon in the Blue Ridge Mountains. (For the record, I missed M74 and M30, but it was still one of my most enjoyable nights of astronomy.) But for various reasons, among them weather, high Sun elevation, and inexperience perhaps, I was unable to located Venus in the middle of the day during the weeks leading up to the March 2009 inferior conjunction. Maybe the sky was too bright, the clouds too thick when I tried to look, or the sky not transparent enough, but I could not find Venus in the middle of the day that March despite numerous attempts.

Can I plausibly disagree then with authorities such as Guy Ottewell, Fred Schaaf, and Alan MacRobert, and say that I think the October inferior conjuction of Venus is actually one of the best? I have been able to follow it more consistently and more closely up to the date of the actual conjunction in October over the years than any of the other four types. This year, I have easily tracked Venus up to now with 10x50 binoculars; I have seen it at 10:30 in the morning when it was directly *below* the Sun in the sky; I have picked it out when lower than the Sun in the late afternoon, and I plan on trying to observe it on the date of conjunction if the sky is clear. The key is blocking out the Sun with an eave, overhang, or building wall and Venus should be easily visible against the blue. I just did this now, a few minutes after noon on Saturday, October 23, when Venus was 10.5 degrees below and slightly left of the Sun, even through some high, thin clouds.

Seeing the razor-thin 1-arcminute wide crescent of Venus in binoculars or a telescope is a joy, and for neighbors or passersby, an unexpected pleasure that adds to the crisp air, blue sky, and colorful trees of this time of year. Your chances of seeing Venus this month, despite its position relative to the Sun, are actually greater than at any other apparition because of the good number of perfect weather days, so get out there and try for Venus under the best daytime skies of the year! With a little practice, it only takes a minute . . .

Eric David
Fredericksburg, VA