Our class was presented with a unique opportunity to meet with Scott Mathews, an MSL Engineer and amateur astronomer. He visited our class class on Thursday, January 6th, to prepare us for the astro-photography/stargazing night at Topanga State Park. He put together a presentation full of pictures taken by amateur photographers including some he took himself and he described some of the techniques used to capture these photos. One picture that I found to be particularly incredible was a picture of the Andromeda Galaxy. The picture above is one example of that galaxy but I was really impressed because a person can sit in their driveway and take a picture of something two and a half million light years away. The process of capturing this image requires a mosaic of images taken with different color filters in order to put the entire picture together. It takes a long time but it ends up as a spectacular picture.
There are many factors to consider when taking pictures of the sky including the atmosphere, surrounding light, and the rotation of the earth. In order to counter-act the rotation of the earth, Scott provided us with "barn door trackers. A barn door tracker, in the picture above, is made up of two boards connected by a hinge. There is a place to attach the tripod on the bottom and the camera on the top. on the end opposite of the hinge, there is a screw with a knob that comes up through the bottom board and when it is rotated, it slowly pushes up the board. Ours was made to raise the top board one degree for one full rotation. In order for this to be true, the distance the screw goes up through the board must be calculated. Then the screw must enter the wood at a certain distance away from the hinge so that the angle of the two boards increase by one degree after one rotation. Fortunately we had a NASA Engineer, Scott Mathews, to figure out all the math behind it and he made a tracker for everyone. The point of the tracker is to rotate the camera opposite of the earth's rotation to take in more light from a static sky which allows the camera to pick up more faint and distant stars at a longer exposure. without the tracker, there wouldn't be as many stars showing up in the pictures and the stars would streak across the sky. The key to making sure the tracker works is to line up the hinge with the north star, which happens to be about the same place as the rotational axis of the earth. To line up the hinge, we attached a straw with glue to look through like a sight on a gun. the straw didn't work very effectively but we also used a bright laser pointer and that helped us line up our trackers pretty well. The tracker knob should be rotated one full rotation per minute of exposure. The tracker isn't a perfect instrument because of the human error caused by aiming the hinge, and small movements when rotating the knob and looseness in the hinge. It is effective up to about a 5 minute exposure and you can still get some awesome pictures with it.
On behalf of the class I'd like to thank Scott Mathews for sharing some of his experiences and knowledge and providing us with the barn door tracker. It was a lot of fun taking pictures of the night sky, especially with tips and tricks to improve our chances of getting a good photo. I'm looking forward to some opportunities for a clear sky so that I can continue practicing and improving.
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