Non-lunar Phases

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 red in the photo is probably due to light pollution from the street lights on Magdalene Close affecting my optics (see the picture above). 

Light Pollution is, in fact, a constant frustration to every amateur astronomer who lives under the overpowering glare of suburban lighting. So to those of you who have those piercing security lights that light up half the village - please give a thought to your poor neighbourhood astronomer, shivering in the cold of the night, fumbling with his knobs and cursing under his breath because the flippin' glare is spoiling his view of Venus ...!

All photographs on this page  © Sabri Zain 2012.