Clear skies at last this evening and here is my latest image capture as twilight descended over Longstanton. After the excitement worldwide over the 'Supermoon' of last week, those of you who read my bLog about it might think that the photograph above is yet another amateur photograph of the perigee full moon. However, the 'supermoon' ended days ago and the more observant among you might note that this is not a full moon but a crescent. You might also happen to notice that it has a brownish-red hue - not the familiar cheesy white of our moon. This is, in fact, not a moon at all but a planet - the rock just before us, Venus. If you had been looking above the skies of Cambridge this evening, you wouldn't have seen this crescent at all - you would have seen what appears to be a very bright star very low on the horizon, to the west. It is so bright, in fact, you would probably have seen it in the daytime (as in my picture below) rather than during darkness, as it rapidly descends below the horizon quite early in the night this time of the year.
What most non-astronomers don't know is that Venus also experiences phases, similar to the lunar phases of our moon. The phases of Venus result from the planet's orbit around the Sun inside the Earth's orbit, giving the telescopic observer a sequence of progressive lighting similar in appearance to the moon's phases. It presents a full image when it is on the opposite side of the Sun. It shows a quarter phase when it is at its maximum elongation from the Sun. Venus presents a thin crescent in telescopic views as it comes around to the near side between the Earth and the Sun (as it does in the picture above and in my video below) and presents its new phase when it is between the Earth and the Sun. The full cycle from new to full to new again takes 584 days (the time it takes Venus to overtake the Earth in its orbit).
You might have noticed a shimmering effect in the video, especially as Venus descended down to the horizon. - this effect is caused by heat currents from the roofs of houses. This is particularly a problem when viewing or video capturing celestial bodies that are found close to the horizon. The problem becomes markedly worse when you're viewing at high magnifications and through Barlow lenses (here, I used a 2X Barlow with a Celestron Neximage CCD imager equivalent to a high-power 6mm eyepiece). Photographs taken of the Venusian surface by NASA probes do show a reddish colouration of the surface rocks, which could be oxidized iron compounds. However, the reddish colour you see in my photograph above is not Venus' true colour - Venus usually appears a very light gray or tan when viewed from Earth (see a second video I took below - this time without using the Barlow lens).
The cloudy weather we've been having here in Cambridge these past few weeks have masked the fact that, for the past week, we have been experiencing probably the most powerful series of solar flares from the Sun this year. NASA has classed these as M-class solar flares - medium-strength sun storms that can unleash powerful blasts of radiation and magnetic solar plasma. The source of these solar flares are what NASA have dubbed "a monster sunspot" - a huge sunspot 60,000 miles in width which NASA have designated Sunspot AR 1476. This Saturday was the first really clear day this month, so I dusted the cobwebs off my long-neglected refractor and pointed her at the sun. This is what I saw:
Sunspot AR 1476 is that smudge a little off-centre on the left limb of the Sun. Now, it may well look like just a little smudge but bear in mind that it's at least 60,000 miles long - that's 8 times the diameter of the planet Earth! Increasing the magnification of the scope with the equivalent of a 6mm eyepiece reveals a little more of the sunspot. The dark core (umbra) surrounded by a larger lighter filamentary outer region (penumbra) are clearly visible.
Increase the magnification with a 2X Barlow even more and you'll see that there are about half a dozen smaller dark penumbrae radiating around the central core.
