[ATMoB-discuss] Venus in UV light

[John Boudreau]

As I'm sure all of you have noticed, Venus appears as an easy naked eye object even in bright twilight shortly after sunset. Visually, currently in a telescope it appears as a bright-white and featureless gibbous-phase disk that's 12.6 arcseconds in apparent diameter. Over the next few months it'll gradually increase in size, and become a fat crescent by late June as it approaches inferior conjunction.

However in the near ultra-violet, out of the visible spectrum at about 360 to 370nm, the clouds do show some structure. Fortunately a webcam or astro CCD camera is sensitive enough in the UV to image at that wavelength if a proper filter is used to isolate that region of the spectrum. I recently bought a Schuler UV filter that normally is used for stellar photometric work, but it also works fine for recording the clouds on Venus with my monochrome CCD webcam and Celestron C11. Here's my first good result with this filter, taken late yesterday afternoon. Scroll about 1/3 down the webpage:
http://home.comcast.net/~jeboud/mercury_venus.htm

The biggest problem is that the atmospheric seeing is seldom very stable during the day and early evening, so this image was taken in much poorer conditions than most of my other planet images (except Mercury). But I'll be trying to image more cloud features as Venus grows in apparent size into the Summer.

---John