by John Walker

Results for 2000 to 2015

compute the hour of greatest elongation

The best time to view Venus in the daytime is when it's near greatest elongation--at the greatest angular distance from the Sun as seen from Earth. If your browser supports JavaScript (and is configured to permit JavaScript programs to run), the following calculator will show you the dates of maximum elongations of Venus for any given year. Due to the geometry of the orbits of Venus and the Earth, the number of maximum elongations in a given year varies between zero (no maximum elongation at all) and two. The magnitude of Venus around maximum elongation is always about -4.1; at maximum brightness Venus is about magnitude -4.4, but maximum brightness occurs when Venus is closer in the sky to the Sun. Year:             Greatest Elongations of Venus Uh, oh. It appears your browser either does not support JavaScript or that JavaScript has been disabled. You'll have to replace your browser with one supporting JavaScript (or enable it, if that's the problem) before you can use this page. The above table lists the maximum elongations of Venus (if any) in the chosen year. Elongations alternate between east and west of the Sun along the ecliptic. Somewhat confusingly, an eastern elongation angle means Venus will be visible in the western sky after sunset, while at a western elongation Venus is visible in the eastern sky before dawn. The "Apparition" column helps sort this out. Maximum elongations occur on the indicated Date in universal time (UTC, or Greenwich Mean Time). Depending on the time zone at your observing site (possibly modified by summer time, if in effect), the maximum elongation may occur on an adjacent date at your location, but since Venus and Earth progress rather slowly along their orbits, a week or so makes little difference in the appearance of Venus near elongation. References Meeus, Jean. Astronomical Algorithms . Richmond: Willmann-Bell, 1998. ISBN 0-943396-63-8. This is the essential reference for computational positional astronomy. The calculation of the time of Venus' greatest elongations is performed using the algorithm given in Chapter 35. by John Walker September, MIM All images in this document are in the public domain and may be used in any manner without permission, restriction, attribution, or compensation. Back links to Viewing Venus in Broad Daylight are welcome.

To compute the UT hour of greatest elongation go to HORIZONS Web-Interface select target body (Venus or Mercury), set the time span to the date indicated above (step e.g. 1 hour), and select 'Sun-Observer-Target ELONG angle' in the table settings.