Hi! I am another British schoolgirl - this blog seems to attract us like bees to honey - and I blog about clothes, books and general nerdy things over at Doxographies. (I know, I know, my username is so pretentious.) I like strange music that tends to leave other people confused, reading, winter and cats. I also like DIYs, astronomy and long-exposure photography, which, as luck would have it, are what this post is about.
DIY MOON PHASE T-SHIRT
Stars seem to be everywhere at the moment, with galaxy prints everywhere from t shirts to socks, but the moon has been sadly neglected. With this in mind, and also with an Astronomy exam coming up, I decided to do a little ‘revision’ by making a t shirt with the phases of the moon on it.
On this t shirt, the large central circle is the Earth, with the smaller ones around the edge representing the moon in different phases. In the picture below, sunlight is coming from the right. The blue circles show what each phase looks like to someone standing on Earth. I’ve also labelled each phase so you can impress people by explaining the diagram to them.
The moon has different phases because parts of it are in shadow, while other parts are lit up by the sun. Interestingly, we only ever see one side of the moon because the way it rotates means the same side is always facing Earth. The ‘dark side’ isn’t really dark, though; at new moon it’s completely lit up.
To make this t shirt, you’re going to need some fabric paint in at least two colours and a pattern, drawn out on paper. I made mine from looking at this diagram and traced it out full size with a black sharpie.
Then, position it inside the t shirt and pin it in place. Hopefully you can see the design through the fabric of the shirt. Use the fabric paint to trace over the design and wait for it to dry, then fix the paint by ironing it for a couple of minutes and you’re done!
STAR TRAIL PHOTOGRAPHY
One really cool thing you can do with a DSLR camera is to take star trail photographs. Because the Earth is rotating on its axis, the stars seem to move in circles. If you have a really long exposure time - 15 minutes or more - you can capture this effect as streaks of light. Astronomers can use these photos to test if a site is good for an observatory- if the star trail photo is clear and there isn’t too much ‘skyglow’ (the reddish-orange colour that street lights give the sky) in the background, it’s a good spot. You can also use star trail photos to calculate how long the sidereal day (the length of a day as measured by stars, which in fact is 23.93447 hours long) is. Stars move almost 15° in an hour, so they would take nearly 24 hours to complete a 360° circle. The little bit of time missing is accounted for by the Earth’s movement through space.
You do need a tripod and a fancy camera with a bulb release for this, unfortunately, so if you want to try some light painting, which you can do with pretty much any camera, scroll down.
First, find somewhere dark - preferably a field, with no nearby houses. If you’re in the northern hemisphere, you need to make Polaris (the North Star) the centre of your picture to get nice curved arcs. Contrary to popular belief, it’s not the brightest star in the sky, but you can find it quite easily. Find Ursa Major, the Big Dipper and follow the green line shown in this picture:
Polaris is the first bright star you see when following this line. If you’re good with constellations, it’s also part of the Little Dipper, or Ursa Minor. In the southern hemisphere, it’s a little harder, because there isn’t one star to point your camera at. I’m not entirely sure, because I have never even been to the southern hemisphere, but you should probably find the Southern Cross and make the centre of your picture a bit below that.
Make sure the camera’s in focus, take the ISO down to 100 and set the camera for an exposure above 15 minutes. Then try not to move too much so you don’t shake the camera and don’t turn on a torch! If you do, the photo might get over exposed and end up plain white. It’s probably a good idea to increase the contrast of your photo after you’ve taken it. Unfortunately, this will bring out any red/orange skyglow, but it also makes the stars look better.
If you don’t have a fancy camera, don’t worry! You can still take awesome long exposure photographs; for example, light painting. Wait until it’s dark, fiddle around with your camera until you find the long exposure setting and dance around with lights; torches, fairy lights, anything. I did this monster with a point-and-shoot camera and a bike light in 15 seconds, the longest exposure available.
You can also ‘draw’ over people’s bodies with the light to get a weird sort of glowing effect.
I think that’s probably enough information about moon phases and sidereal days to keep you going for a while, but if you’ve got any questions, feel free to ask me. Have fun, and try not to get pneumonia if you sit out all night taking pictures of the stars.
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