Viewing Venus

In Fall 2005, Venus will be very bright in the western sky each evening. Its size and phase will change dramatically as it `catches up' with the Earth.


This table provides simulated images and other data for Venus every Wednesday this semester. Each date links to an image showing how Venus will look that day. The altitude column gives the angle between Venus and the horizon as seen from Honolulu at 19:30 HT (7:30 pm); each number is also a link to a map of the sky. Venus will be setting in the west; to get the best views of the planet, we need to observe it as early as possible. The diameter column gives the apparent diameter of the planet; note the rapid increase in size as Venus approaches the Earth. Finally, the phase column gives the angle between our line of sight toward Venus and the direction of sunlight falling on the planet. At the start of the semester, Venus is gibbous, but by the end it will be a crescent.

Date Altitude
(degrees)
Diameter
(arc-seconds)
Phase
(degrees)
08/24/05 17.9 14.1 57.9
08/31/05 16.9 14.7 60.8
09/07/05 16.0 15.3 63.7
09/14/05 15.1 16.1 66.7
09/21/05 14.4 16.9 69.7
09/28/05 13.9 17.8 72.8
10/05/05 13.6 18.9 76.0
10/12/05 13.6 20.1 79.3
10/19/05 13.8 21.5 82.7
10/26/05 14.2 23.0 86.4
11/02/05 14.8 24.9 90.3
11/09/05 15.4 27.0 94.6
11/16/05 15.9 29.5 99.3
11/23/05 16.1 32.5 104.6
11/30/05 15.8 36.0 110.5
12/07/05 14.7 40.2 117.5

VENUS IN THE AFTERNOON

Venus is bright enough to see during the day if you know exactly where to look. The best time to look this semester is in the afternoon when Venus crosses the meridian, an imaginary line running North to South across the sky. At this time Venus is as far as possible above the horizon. In addition, it will be due South, so you know which compass direction to look. The table below gives some dates and times when Venus crosses the meridian, as well as its altitude at that moment. In general, you won't be far off if you look any time between 15:00 and 15:30 HT (3:00 to 3:30 pm).

Date Time
(HT)
Altitude
(degrees)
09/28/05 15:08 49.2
10/12/05 15:17 44.8
10/26/05 15:28 42.2
11/09/05 15:35 41.7
11/30/05 15:30 44.2

It's fairly easy to find Venus using binoculars; face due South and scan the sky at an altitude (angle above the horizon) of 45°. (If you're not sure which way South is, East-West Road on campus actually runs almost exactly North-South; it should be called North-South Road!) Venus will be a brilliant point of light in the daytime sky. Once you've found it with binoculars, try looking without them. If your vision is good, you may be able to see Venus with your naked eyes. Orange or red-tinted sunglasses can help by increasing the contrast between Venus and the blue sky.

WEB RESOURCES


Roberto H. Méndez (mendez@ifa.hawaii.edu)
Last modified: October 24, 2005
http://www.ifa.hawaii.edu/~mendez/ASTRO110LAB05/venusviewing.html
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