June 28, 2010

The latest sunset of the year, a great time to look for the “Belt of Venus

This evening, Monday, June 28th, marks the latest sunset of the year. The summer solstice, the “longest” day of the year was a week ago. The earliest sunrise at latitude 40 north was June 14th. The days seem to continue to grow longer after solstice because more people see the sunset than the sunrise. This evening’s sunset happens at 9:10pm and from this evening forward the sunsets will come a few seconds earlier each evening. Our sunsets will continue to occur at 9:10pm through July 4th, happening a few seconds earlier each evening until July 5th when the sunset slides all the way back to 9:09 pm!
While you’re enjoying these late evening sunsets I have a simple and fun observing exercise for you. Turn your gaze away from the sunset in the west and look to the east and watch for the “Belt of Venus”. This is a very subtle effect and you’ll need a clear, low, open horizon to the east.
Look for a pinkish belt of color above a darker blue on the eastern horizon. To see this effect you need to be watching in the moments immediately following sunset. The pinkish glow is the refracted light of the sunset which is now 75 to 100 miles west of you. The dark bluish belt is the earth’s shadow heralding the coming nightfall.
We saw a beautiful display of the Belt of Venus on Sunday evening but the memory card on my camera was full. I did manage to take a couple of images with my mobile phone but haven’t figured out how to download the files to my laptop!

The image above was taken by UK amateur astronomer Pete Lawrence in Selsey, UK. Click on the image to open it.
I learned of the “Belts of Venus” in Tony Flanders column in S&T
Next: Morning Moonwatching as the “old” Moon turns “new”.
Clear skies,
Mark, the StarGeezer

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