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HM Nautical Almanac Office: Transits of Venus

Introduction

An observational overview of the transits of Venus in the telescopic era as well as the six centuries or so at either end of this period is presented. The table below gives the dates of these rare phenomena covering the interval from the 11th century through to the 27th century. More detailed information can be found on a specific event by following the appropriate link in the table below. Transits with links in pale yellow boxes have more detailed information than those in the cyan boxes. The dates given in the table are Julian dates before 1582 AD and Gregorian dates thereafter.

† Although the two inferior conjunctions of 1145 November 26th and 1388 November 26th do fit the pattern for the recurrence of transits of Venus, the minimum separation between the centres of the solar disc and Venus is larger than the sum of the semi-diameters of the Sun and Venus rendering a geocentric transit impossible.

Other Information

Exclamation mark Safety first - Observing the Sun Exclamation mark

Observing the Sun is potentially very dangerous unless you know what you are doing. Unlike a total eclipse of the Sun, there is no phase of totality during a transit of Venus. The drop in light from the passage of Venus in front the Sun is negligible, amounting to a mere 0.1%.

Never look directly at the Sun with the naked eye. There are no pain receptors in the retina and irreparable damage to the eye or even blindness caused by observing the Sun without adequate protection can be done with only a few seconds of exposure. The effects of this damage will only become apparent several hours later.

Always use proper certified filters to protect your eyes. Solar eclipse viewers with a neutral density of 5 or more, made of black polymer or aluminised mylar may be used. Such viewers reduce the harmful visual and infra-red radiation to safe levels. In the European Community, the viewers should carry the "CE" mark denoting certification under Personal Protective Equipment Regulations (European Council Directive 89/686/EEC). They should also be checked thoroughly for damage. When putting the viewer on or taking it off, remember to turn away from the Sun.

Never look directly at the Sun through telescopes or binoculars or similar optical devices. If a telescope or binoculars are used then the projection method can be adopted using two pieces of card. The first piece of card casts a shadow behind the telescope. The image of the Sun is then projected onto the second piece of card which lies in the shadow of the first. This allows several people to view the transit. Never sight along the side of the telescope to point it at the Sun.

DISCLAIMER: Neither UKHO, its employees nor anyone else involved in the creation or production of this material shall be liable for any direct, indirect, consequential, or incidental damages arising out of the use, the results of use, or inability to use this material even if UKHO has been advised of the possibility of such damages or claim.

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Last modified: Friday, 01 June 2012 at 11:53:51 BST