Jenkins-Of-Ewelme Web Site

Position of Planets 1

This dynamic page is intended to demonstrate the power that can be embedded within a web page, by inserting some additional program code (JavaScript) that your browser can understand (designed for Internet Explorer, and others may not show chart). Because of an interest in Astronomy, I have chosen to use some calculations to show  the actual positions of the Sun, Moon and planets as they are NOW with respect to my telescope position in Ewelme. Although the results are accurate from here and have involved some quite complex algorithms, they are probably perfectly adequate for the area of Buckinghamshire, Berkshire and Oxfordshire or even wider. 

To make this information as practically useful as possible, I have just shown the Azimuth (compass direction) and Altitude (angle above the horizon). Both these angles are shown in a rounded decimal degrees form, although astronomers often prefer these to be shown in degrees, minutes and seconds.  However, unless one is using this real time data to control the position of a telescope, the whole degrees part should be quite enough for just trying to identify whether a bright point in the night sky is a planet or a star.

Either use a compass to find the Az angle shown with respect to North (0 degrees), or orientate yourself using the North 'pole' star (Polaris), remembering that East is 900., South is 1800., and West is 2700, As far as Alt is concerned, remember that 00 is the horizon and 900 is directly above your head. I'm sure you'll realize that if a reading is negative, it is below the horizon, but you should be able to deduce whether the object is tending towards rising (-90 to 0) or has just set (0 to -90).

Points of Interest

When the Moon phase = 100 %, the moon is full. 0% is a new moon. Between 0 and 100 the Moon is waxing (getting lighter from right to left), and between 100 and 0, it is waning (getting darker from right to left)

Because Venus (and Mercury) orbits between the Earth and Sun, it also goes through phases, which can be recognized using a small telescope.

"Midday" is usually recognized by the fact that the Sun is at its highest point in the sky (crosses the Meridian = South). See what time the Altitude of the Sun reaches its maximum before falling towards zero again (sunset). You might be surprised that because we are at a longitude of about 1 degree West, we see this occur 4 minutes before 12 o'clock, because midday at Greenwich (GMT) is really 4 minutes late in Ewelme!!

The Sun is said to rise in the East (90 degrees) and sets in the West (270 degrees). This is in fact so, when the day equals night at the Spring and Autumn Equinoxes. Notice that at other times, the sun rises North of East and sets North of West during the Summer (longer days) and rises South of East and sets South of West during the Winter (shorter days). It reaches its extremes at the Summer and Winter Solstice.

At midday (-4 mins) on the day of the Summer Solstice (mid summer)  the Sun will be at its annual highest. In fact it will be at the same angle as our Latitude here in Ewelme i.e. 51.6 degrees.

The apparent path the Sun takes across the sky is called the Ecliptic, but remember that it is the Earth orbiting a 'static' Sun which actually gives this effect. Since the planets, including the Earth and Moon, all orbit the Sun in about the same plane, it means that they basically all follow the path of the Ecliptic as well.  So, don't expect to see the Moon or any of the planets if you are facing North. However, there is a wonderful 'photograph' being sold locally of the 'Dreaming Spires' of Oxford, taken from South Parks looking North. Above the domes and towers a full moon completes this attractive scene!  That devious photographer obviously hadn't read these notes!