July 23, 2019

AstroEvent of the Week: February 2nd-8th, 2009; Spot a Daytime Venus!

A Daytime Venus Shortly After Occultation. (Video by Author).


Astronomy isn’t just restricted to a night time activity. Many folks do not realize that objects such as the Moon can be spotted even in broad daylight. This week, I give you a fun daytime naked eye challenge; spotting Venus in the daytime.  No special equipment is required; just a sharp set of eyes and persistence. Venus is the third brightest natural object in the skies, and surprisingly easy to spot once you’ve seen it. Since it recently passed greatest eastern elongation on January 14th, it’s well placed for afternoon sightings. The best way to do this is to first spot Venus in the west, right after sunset. It’ll be unmistakable as a bright, shinning beacon, even from urban areas. Note or mark your position, especially in relation to a foreground object, such as a telephone poll or apex of a house roof. The next night, clear skies willing, go out again to the same position about an hour before sunset and look about a hands width up and to the left of the previous nights’ position. There it is! If you can block the Sun while doing this, so much the better. Deep, clear blue skies are also a help. (see below) I’ve seen Jupiter and Mars near opposition during the daytime in this fashion. I have yet to spot, (although it’s theoretically possible!) Sirius or Mercury at greatest elongation. Still can’t see it? Sometimes a brighter object, such as the Moon, can help as a guide. On February 27th-28th the waxing crescent Moon will be very near Venus worldwide to aid in sighting, and even occult Venus for a privileged few (penguins?) off of the coast of Tierra del Fuego. Good luck!

The Astro-term of the week is Atmospheric Extinction. This is your enemy during Venus daytime sighting attempts. The empty sky, day or night, has an intrinsic brightness. Extinction is caused by the scattering of light through our atmosphere, and the more suspended particulate matter there is over head, the less you’ll see. Skies over urban areas typically have a white, washed out look due to extinction, while rural, high elevation areas have a deep blue glow. Yuck, atmospheric extinction!

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