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Astrophoto of the Day: Venus waning

Last night was clear once more, and Venus - so bright and high in the sky - was a tempting target, and I wanted to test the setup changes I made to my telescope's drive. So: a new astrophoto!

Keep an eye on the western sky just after sunset for the next few weeks, because Venus rises to its greatest evening elongation - until 2017! - on January 14. This means it'll stand the highest in the sky on that night, and it'll be approximately quarter-phase. This is because, at its highest or greatest elongation, it stands at its farthest from the Sun from the perspective of the Earth. When it's closest to Earth, it's between us and the Sun, so then it's at a phase comparable to "new Moon." When very near the Sun from our POV, it's nearly full. In my photo, notice how the planet is a bit larger than quarter phase: It's waning gibbous phase right now.

So even though Venus goes through phases like our Moon, it's for very different reasons: For example, the Moon is full when on the opposite side of the Sun from the Earth. Similarly, Venus is in waxing phase in the morning sky and waning phase in the evening sky.

Optics details: Taken with a Meade 12" LX90 GPS telescope and a Meade DSI-III astro-imager at prime focus using an f/6.3 focal reducer, resulting in a focal length of 76.8" or 1951mm. Screwed into the imager's barrel was an Orion adjustable polarizing filter set at about 40% to reduce glare (not quite enough; considering using my solar filter next...).

Image is approximately 1/10 second. During processing, I cropped the dark area around the planet without reducing image size, decreased brightness by 60%, and removed color saturation to eliminate false color due to extreme brightness.

Here's how Venus would photograph if one had a telescope in orbit around the planet (a bit fuller, though):

Click the image to see the wiki article.

Still loving this whole digital-astrophotography thing.




( 3 comments — Leave a comment )
(Deleted comment)
Jan. 13th, 2009 10:29 am (UTC)
Heh. Venus' phases don't seem "natural" to the newly inintiated, because they're sort of the opposite of the Moon's (or any of the Outer Planets).
Jan. 13th, 2009 03:30 pm (UTC)
the Milky Way
not about Venus, but this is interesting:
The jumbo Milky Way and other research treats: Bigger, denser and more thoroughly spun — that's the new Milky Way (http://www.siliconvalley.com/latestheadlines/ci_11384152?nclick_check=1), or at least the new picture that astronomers have gotten by mapping our galaxy in a more detailed, three-dimensional way. A team working out of the Harvard-Smithsonian Center for Astrophysics announced Monday that the new measurements reveal the Milky Way to be 15 percent broader than thought, with 50 percent more mass, spinning at about 600,000 miles per hour, 100,000 mph faster than previously calculated. Oh, and it seems to have four spiral arms instead of two. The new measurements put the Milky Way on a par with neighboring Andromeda, which is nice if your self-esteem is tied closely to the size of your galaxy. Unfortunately, it also means that the two will meet in a cosmic collision somewhat sooner than expected. Not to worry, though — that's still something like 7 billion years away and the sun will burn out around then anyway.
( 3 comments — Leave a comment )