Two weeks ago I did some actual science.  I went to Giant Sequoia National Monument with an astronomy class, taught by Richard Nolthenius of Cabrillo College in Aptos, California.  I used my telescope, a shortwave radio, and a voice recorder.

That’s my telescope above, made of cardboard and plywood.  I didn’t make it myself, but I got it from someone who got it from someone, who made it.  It’s a newtonian reflecting telescope with a 12.5 inch diameter mirror on a Dobsonian mount.

We observed a lunar grazing occulation, which is when a star skims the edge of the moon and blinks on and off.  If you know your position on the earth (i.e. with GPS) and the exact time, you can do the math and figure the position of the moon very accurately, which is useful.  The Moon slowly moves across the sky against the stars (making a complete path once a month) and at certain times and locations on the earth, it gets near a bright star that makes a good reference for small telescopes. I had a shortwave radio tuned to a universal time signal, beeping in the background as I looked through the eyepiece of the telescope at the moon.  When the star disappeared, I would say “D”, and when it reappeared, I would say, “R”, into a voice recorder.  The star blinked on and off several times as the mountains and valleys of the Moon passed in front of it.  You can have other observers only a few meters away and get different timings because of the sharp shadow of the Moon’s surface as it passes you.


The teacher had a more advanced setup, recording with a video camera.

Later we will analyze the video and voice recordings and send the timings to an organization (IOTA) that will use the data to get an accurate distance and position to the moon and it’s surface features.  Even amateurs can make contributions to science this way.

It’s fascinating to observe a graze– you tend to think of stars as unchanging, always on, but then you wait at a special time and place, see the star get closer and closer to the moon, then suddenly turn off, and then on again and off and on, several times.  If you are using a voice recorder like I was, you have to be very alert and react quickly to get accurate timings.


After the graze, I observed  star clusters, galaxies, and nebulae through my telescope in the clear Sierra skies. It got bitterly cold though, it was 6000 feet altitude in mid October, and in the morning the dew had frozen.


During the day, we walked through the Trail of a Hundred Giants.   It was alarming to see so many brown and felled trees.  The drought has prevented pine trees from producing enough sap to protect them from pine bark beetles.


It was a long drive, but well worth it, if only for Rick’s crepes.

For more information on lunar grazes, see Rick’s graze page here.

For more of my photos of the trip, see my flickr album here.



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