I am new to astrophotography. You could fill encyclopedias with what I don’t know about it, but I’d like to share what I’ve learned. If you are interested in trying your hand at this sleep-depriving endeavor, I will go through a few of the basics.
-Camera that will take long exposures
-Remote shutter release
The Three Main Problems and Their Solutions:
The first problem (It’s dark out there) is all about the lens. A lens with a large aperture F1.4 to F2.8 will do. Anything smaller will not let enough light in before the stars have moved. Also, on a digital camera, you will want to set your ISO to at least 400 (preferably 1600). Every camera handles higher ISOs differently (some better than others), so you will need to experiment to see how high you can go without introducing noise. Since stars emit light, they will show up in your long exposure, but foreground objects (trees, mountains, etc…) usually do not. This is where the real fun begins. I think it is so cool that you can shine a flashlight on any object you want to show up in the photo. You can actually paint objects with light while the exposure is taking place. Take a look at the next two photos. Both photos are exposed for 25 seconds, but the second shows what happens to the trees when light is run along them during the exposure.
This brings up the second problem, the earth is spinning. If you expose your photo longer than 20 to 25 seconds the stars will appear as small dashes. Just experiencing this gives you a first-hand look of the rotation of the earth and how quickly it makes the stars appear to move across the sky. You have two options here. The cheapest option is to keep your exposures under 25 seconds and use a fast lens (f1.4 – f2.0). The longer you expose your photo, the more stars you will see in your photo. To get a longer exposure you will need a motorized tripod mount that compensates for the rotation of the earth. A sky tracker mount can run from $300 on up. The disadvantage of a motorized mount, is that although the stars will appear correct, any foreground you want to help your composition will be blurred from the movement. At this point in my foray into astrophotography, I prefer shorter exposures and some clear foreground objects. Experts in this may have solutions to the blurred foreground with the tracking mount, but I haven’t figured it out yet. The following photo shows what happens if the exposure is a little too long (without a tracking mount). If you look closely, you can see that the stars are small dashes. The second is a time lapse where you can see the movement of the stars.
The third issue is focus. It is surprisingly difficult to get the focus right. Considering that a large aperture lens has a very shallow depth of field, getting both the foreground and the background in focus is a real challenge. Since most affordable, modern lenses don’t have a distance scale, your best bet is to turn off autofocus. Focus manually to infinity (or just short) in the daylight, then use a focus lock if the lens has one (or use a small piece of tape to lock it in place).
There are a number of further challenges, such as: City lights create a light bubble that can’t be escaped without getting at least 50 miles away from an urban area. The moon is super bright and will wash out any long exposures. The weather will likely not cooperate, but a few clouds can add interest. Even in good weather, dew can form on your lens. It can get really cold out there. And lastly, astrological events like meteor showers are not all that predictable. Even taking 25 second exposures (one immediately following the previous) for hours, doesn’t guarantee you a shot of a meteor.
It is worth noting that although the tracking mount is also needed for the solar eclipse, most of the concepts are opposite. You would need a solar filter and can use a slower lens. I won’t get further into the eclipse shooting, since I don’t live within the path of the upcoming event. If you do, there are some great resources out there.
Just getting out there, where the stars are clear is worth the effort. Go stare at the stars and take some cool pictures!