Saturday, 3 March 2007

A thousand sunsets

Now we will take a glance into an entirely different part of the spectrum. A total lunar eclipse was visible from my location (and almost half of the world). Here is one of the photos I took during totality using a Canon 350D digital SLR and a 300mm f/5.4 lens mounted on a simple altazimuth tripod. Exposure time is 1/4 sec, ISO 1600. Unfortunately it was a windy night so most of the images are blurry.

I thank my brother for letting me use his photo equipment!

Amateur astronomy is another hobby of mine, a demanding hobby requiring patience and endurance for staying outside in the night to fight the elements (and mosquitoes!) A hobby which doesn't like modern "achievements" like "light pollution".

Update 13/03/2007:

"OK, how dark is this?" You may ask. If you are familiar with photography, by noticing the ISO and shutter speed settings, you have your answer. If not, think of the following: The full moon is sunlit so it will require camera settings similar to a normal sunny scenery. This is true. Using the same lens and f/ ratio, a normal full moon will require 1/500 or 1/1000 sec at ISO 100 or 200. Pretty close to normal daylight photography. Here we have an eclipsed moon. Note the use of ISO 1600 and 1/4 sec exposure time. Compare that with say ISO 200 at 1/1000 sec. That implies 8 by 250 that is 2000 times less light from Moon during a lunar eclipse!

Hevelius' drawing of Leo, 1690

For the more familiar with Astronomy, 2000 times less light is about 8 stellar magnitudes drop. Full Moon shines at -13 mag. The stars (from down right to upper left of the eclipse photo) 56 Leonis (mag 5.8), 59 Leonis (mag 5.0) and χ Leonis (mag 4.6) will be very hard to notice due to the brightness of a Full Moon. During the lunar eclipse these three dim stars share the same frame with the moon. A normal observer under dark skies (no moon) can reach stars of mag 6, so 56 Leonis is near the visibility limits.

And another detail: I used the Daylight white balance setting of the camera. Auto white balance would produce a false-colored Moon. As I mentioned before, Moon is sunlit after all.

The Astronomy lesson is over. Just stop and think for a moment that the golden brown colors of an eclipsed moon is the combining result of all the sunrises/sunsets here on Earth... You can see all of them at once...

Strong signals and clear skies!

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