Chris McKitterick (mckitterick) wrote,
Chris McKitterick

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.


Tags: astronomy, telescopes

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