Venus… -6 Days Till Inferior Conjunction

We are now within a week of Venus‘ inferior conjunction. From my backyard there is no way to observe Venus at night any more (too many trees on the horizon). As a result, all observations are during the day, usually late in the morning or late in the afternoon. The hardest part after finding Venus (I don’t have a computerized telescope so I need to find Venus in binoculars first) is trying to see Venus on the screen on my laptop in broad daylight.

As Venus marches (or orbits) towards inferior conjunction, it is gradually appearing larger and thinner. This is obvious to telescope users. Even small binocular users can easily see Venus as a crescent. For those with great eyesight, it may even be possible to see Venus as a crescent with just your eyes.


Below is a direct comparison between Venus from today and 2 weeks ago. On Mar. 8.06 UT, Venus was 0.332 AU from Earth (30.8 million miles or 49.4 million km). It was 50″.2 arc seconds in diameter and 12.6 percent of its Earth-facing disk was illuminated by the Sun. At the time, it was also easy to observe being 28.7 degrees from the Sun.

Today at Mar. 21.73 UT, Venus was 0.286 AU from Earth (26.6 million miles or 42.6 million km). The closer distance means Venus is now 58″.3 arc seconds across (or 16% bigger). As can be seen below, much less of the disk is illuminated (2.4%). The observation is also much tougher now that Venus is only 12.7 degrees from the Sun.


At its closest to the Earth on March 27, Venus will be 0.281 AU from Earth (26.1 million miles or 41.8 million km). Only 0.97% of its 59″.3 arc second Earth-facing disk will be illuminated by the Sun. Hopefully at that time Venus will appear as a ring when its atmosphere refracts sunlight around its edge.

About Carl Hergenrother
I am a professional astronomer specializing in the study of comets, asteroids and meteors. This blog will focus on my professional and amateur work in this field

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