Shooting astronomical subjects, known as “astrophotography”, can be a lot of fun to dabble in. Some of the common subjects that can be photographed using these techniques include meteor showers (of which we usually have several good showings each year), different phases of the moon, space shuttle flybys (sometimes coupled to the International Space Station, or sometimes the shuttle and space station as two distinct, separate entities!), comets, and even eclipses (on those rare occasions). The possibilities are endless and limited only by your availability and equipment, and your viewing location.
Regarding equipment, the only requirements are a camera body, a telephoto lens, and a sturdy tripod. The camera body should be able to be set to ISO 400 and should have a “Bulb” (or B) exposure setting. You should also have a remote shutter release (either wired or remote) to minimize “camera shake” when making exposures. The telephoto lens can be any ordinary telephoto lens, and the focal length best for the image will vary, depending on the subject. For meteor showers, one of the most common astrophotographical subjects, you don’t want a very long telephoto lens; a lens in the range of about 35mm to 55mm seems to be the best. This “smaller” lens will give you more coverage of the area where you are expecting to see the meteors as they streak by. For shuttle flybys or for lunar/planet images, you will want a larger telephoto lens, often the bigger the better. As for the tripod, the heavier the tripod, the better; you want the sturdiest you have to shoot these long exposures.
Exposures can vary depending upon the subject you are trying to photograph. The larger or brighter the subject, the less exposure time you will need. Conversely, if you are shooting meteor showers or are shooting “star trails” or the “space shuttle trail”, then you will want to make longer exposures. This is necessary because these are either much smaller or brighter, or, in the case of meteors, will last only a brief instant, so you want to have the exposure running for several minutes (in the range of about 4-10 minutes) to increase your chances of getting a meteor in the exposure. The only dowside to these longer exposures is that electronic “noise” becomes more pronounced as the exposure time gets longer (but try anyway, you can always delete the images if they are too noisey). When shooting these subjects, I have found that a large Aperture (i.e., f/4, or so) works quite well.
When shooting astrophotographical subjects, it is imperative that you shoot LOTS and LOTS of exposures! And if you find that the shutter time needs to be either shortened (too much light being gathered from other sources during the exposure) or lengthened, don’t hesitate to experiment! If you shoot digitial, remember that it costs you the same to shoot 100 images than it does to shoot one image. But the most important thing to remember is to HAVE FUN!!! That is what this is all about.
So the next time you are photographing a heavenly body (of the spatial type), try these tips to see if they work for you. If you have some other techniques you’d like to share with everyone, just e-mail me your suggestions and I will include them in a Blog posting.