Venus in 2005

Dia 1: Times for the setting of Venus and the Sun from April to December 2005. Click for an enlargement

Venus is officially an evening object. That is to say, it sets after the Sun.

But from the northern hemisphere, when conjunctions take place this late in the season of spring (Venus superior conjunction March 31), the planet is not well placed for observation with the unaided eye.

This is because the interval between the setting of the Sun and Venus is small despite the planet's growing elongation.

Dia. 1 shows the times of setting for the Sun and Venus from April to December 2005. Around the middle of June Venus will be setting about 1h 30m after the Sun; but twilight is so strong at this time of year from the latitude of the Northern Isles so that Venus will only be visible against a bright sky low down in the NW.

Up to this time, Venus has had a superior declination to the Sun. However, by the end of June the Sun will gain in ascendancy over Venus and the interval between the setting of the two bodies will narrow.

By late October Venus will be very low in the sky indeed.

Greatest eastern elongation will take place on November 3.

By the middle of the same month the planet's declination will begin to increase so that by December it will appear as a brilliant evening star in the SSW. I have used the term "evening star". Scientifically the word "star" is a misnomer, of course, but it is a term by which Venus has been known for centuries.

Contrail 2005 April 26 09h 22m UT. At the time Venus was between the Sun and the margins of the trail.

Fig 2 Contrail 2005 April 26 09h 44m UT. Note the trail has expanded and moved westwards which was opposite in direction to the wind at much lower levels. It was possible to observe Venus between the breaks in low cloud but the trail had by now engulfed this area of sky.

Telescopically, Venus is seldom out of range for more than a few days.

Once again it must be emphasized that great caution is needed when observing close to the Sun. On April 11 (elongation 3°) Venus was observed with a 80mm refractor using an extended "dew cap".

On 26 April (elongation 7°) no cap was needed but nothing could obviate the condensation trail (Figs. 1 & 2) which sensibly ruled out further observations.

Some interesting close conjunctions with other planets will be noted nearer the time of the events.

A footnote to digital photography of the sky.

Comet Machholz is still observable passing almost through the zenith at around 22h UT. (See archives for location map.)

A few observers have noted when trying to image objects high in the sky using SLR digital cameras that they accumulate some particles on the screen. This is inevitable especially when changing lenses with the camera pointed towards the zenith.

I have to admit that this has caused me considerable problems over the weeks I have been tracking Machholz. Clearing the protector plate requires mirror lockup and the operation is tricky, requiring proper equipment and skill. I would therefore urge all observers to change lenses only with the camera pointing to the ground.

I find the problem of particles tends to be understated by the manufacturers and reviewers of digital SLRs.

It is one of the drawbacks of digital photography not encountered to the same extent with film, for obvious reasons.