FAQs - terroba

Q. Who took all of the photos and movies in the galleries? A. I did, or my students did. Every photograph is signed by the photographer at the bottom. There are no "borrowed from the internet" photos. Q. What kind of telescopes were used to take the photos?

A. At Oxford college we have a variety of telescopes, ranging from 6 to 11 inch Schmidt-Cassegrain telescopes. (You can find a listing of our telescopes on the equipment-telescopes page.) It's very important to have a range of different telescope sizes because objects in the night sky are not all the same size. In general, the bigger the telescope, the more it zooms in. We don't always want or need a high 'zoom' for imaging. For instance, to view the entire Moon requires a low magnification telescope, which trying to make out the atmospheric bands on Jupiter requires a very high magnification telescope. In addition, to photograph the largest objects in the night sky like planetary nebula and the Andromeda galaxy, I have also recently purchased two Newtonian type telescopes (6 and 8 inch diameters) that are of much lower magnifications than the Schmidt-Cassegrain types.

Q. What kind of cameras are used to take the photos?

A. We use two different types of cameras that can be directly mounted into the eyepiece holder of the telescope. For imaging very small objects like planets or craters on the moon we use a color astronomical camera called the ZWO ASI120MC. It costs less than $300 and is extremely versatile. We had used the popular imaging source DMK cameras previously, but the new ZWO camera has some added features like being able to crop the image size during recording. This can significantly speed up the data acquisition rate resulting in much better planetary imaging. We also have several Canon DSLR cameras, the T4i and the T5i. These are normal consumer level cameras and are used to capture images that require a larger field of view than the ZWO camera. Examples include photos of the Moon, star clusters, galaxies, nebulae, the Milky Way and the Sun.

Q. Does Oxford college have an observatory?

A. No. When the students and I go out observing, we just walk over to the college soccer field and set up the telescopes. There are no lights on the field, but there are some nearby. This is not a problem for lunar or planetary imaging, or for photographing star constellations. When we need really dark skies to photograph the Milky Way, dim star clusters or nebulae, we drive 20 minutes further away from Atlanta to the very dark skies of the Charlie Elliot astronomy field.

Q. Do you use Photoshop or Gimp to "clean up" you images?

A. It depends. For planetary imaging, we use Registax6.2 (if it's an .avi file) and the basic functions of Brightness/Contrast/Sharpening in Powerpoint. For imaging of deep sky objects we use Gimp and sometimes Deep Sky Stacker. For star trail images we use StarStax.

Q. Can I download or use your images for personal or educational use?

A. Yes you can. All images can be downloaded at full resolution simply by clicking the download icon in the bottom right corner of each photo when displayed. Note that all photos have dimensions of 8x10 so that if you print them out as 8x10" photos they will appear exactly as shown w/o cropping. I only ask that if you download images you leave a quick comment on the comment page describing what you're doing, and thanks!

Q. I noticed that you have a lot of star trail images, is there some educational use for those?

A. Absolutely there is. First there is the obvious observation that the stars are moving because the Earth is rotating, but more importantly it's a great way to see the true colors of stars. All intro textbooks talk about stars having different colors, hotter stars are bluer and colder stars are redder. Students read and memorize this, but the problem comes in when they look up at the sky themselves. Clearly, all stars look white, so what's going on? The truth is that stars appear white to us because they are so dim and our eyes can't see their colors well. To prove to them that stars have colors, I take my students out and take long (30sec) photos of stars with a DSLR camera. The stars are small dots, but they can begin to see their colors. A better way to see star colors is to collect a short sequence of photos and stack them together so that the stars make lines, which are much bigger and easier to see than dots. That is the power of star trails photography. For example, check out the star colors in this photo from my back porch, the colors (and relative temperatures) are easily visible. Sometimes we zoom in and purposefully defocus the camera so the star trail lines are thicker, like in this photo. It's a very simple process to make trails from photos, in fact the program Starstax can do it with one (yes, one) click of the mouse.

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