On Feb 13, 8:16*am, Nick wrote:
These apparitions of Venus happen at regular intervals. *There is a
"resonance" between the orbits of Venus and Earth - 8 "Earth" years are
almost exactly 13 "Venus" years - so that conjunctions (when Venus
appears to pass between us and the sun [inferior], or on the far side
[superior] ) and elongations (when it appears to us at its furthest from
the sun) can only occur in one of five months of the year.

Interesting - by looking at fourmilab.ch/yoursky I looked at the
evening sky 13 years before several recent appearances of Venus and
noticed that it was there again, in a very similar position.
ISTR all prominent appearances of Venus being in the earlier part of
the year - February through to about June - would this fit in with the
elongations only occurring at certain times of year?

By late March it looks like Venus will be visible until 2230 GMT /
2330 BST - four hours after sunset and thus visible in complete
darkness for a good while.

Nick

The spring elongations are the most easily observed because the
ecliptic (the plane of the earth's orbit) makes a large angle with the
horizon (over 60°) around sunset. This applies to the waxing moon and
to all the planets. In the autumn the angle is much less (typically
14°) and Venus will be much lower in the sky even if 45° from the sun
in azimuth. On the other hand when Venus is west of the sun (i.e. to
the right of it) it is most prominent in the autumn but before sunrise
so far fewer people see it. This year greatest western elongation
occurs in mid-August so the planet will be prominent in the morning
autumn sky as well. If inferior conjunction takes place near the
winter solstice (e.g. Jan 15 2006) Venus is poorly seen at both
eastern and western elongations.

Tudor Hughes, Warlingham, Surrey.