Sky has fascinated people from the dawns of civilization so it is no wonder that there are a lot of people today still passionate about astronomy, that spend the nights gazing at the stars. If you like observing the sky and don’t have a fancy telescope, but you do have a DSLR camera, here are a couple of tips on how you can use it to get nice pictures of the stars.
What lens is the best?
Here it depends on what you want to photograph. If you want to take pictures of the galaxies, stars or the moon a 200mm or more telephoto lens is needed. A wide lens can be used to get more panoramic images of the sky. The faster the lens the better. Regarding the aperture, a f/2.8 lens is always better than a f/5.6 as it allows more light to enter the camera in the same amount of time.
What can I photograph?
If you don’t have a telephoto lens, you probably won’t be able to zoom too much on the objects, but you can still catch panoramic images of the constellations, meteor showers, or astronomical events like lunar eclipses or comets. You can also try taking a wide image of the sky using a long exposure (try 30 seconds or more using ISO 400 or 800 at 18mm) to catch the star trails produced by the movement of the Earth (the apparent movement of the stars.)
As a word of advice do not try to photograph solar eclipse (or the sun directly) using your camera, without special equipment, as the brightness of the sun can destroy both your camera and your eyes, even if you just look a brief moment in the sun directly.
If you own a 200mm or more zoom lens, you can start by photographing the moon. As it is quite bright you can take photos of it at 200mm even without a tripod, but one will come in handy for sure. You can take shots of the moon in it’s different stages of the lunar cycle, and spot the larger craters on it’s surface.
Other things you can try capture are the planets, don’t expect to see too much detail trough a normal lens, but in some cases a 200mm lens can be enough so you can spot the moons of Jupiter.
Galaxies, star clusters and nebula’s can be also photographed if you have a sensitive sensor (that allows high ISO) and a fast telephoto lens (e.g. f/2.8), although to get some details you will need to take multiple long exposures and then stack them manually or using software like DeepSkyStacker. The reason for stacking is that, without having a tracking mount that follows the earths movement, you cannot take longer than 3 or 4 seconds long exposures until the stars apparent motion on the sky leave you with trails in the image. So you need to stack a lot of shorter exposures to get as much light detail as possible. For the faintest of objects you may need hundreds of exposures.
The brightest and easiest to catch deep sky objects are the Andromeda galaxy and the Orion Nebulae. Both are visible to the naked eye with a size similar to a star, but large part of their surface on the sky is faint so you can catch it only trough a long exposure / stacking, or by using a telescope.
To see the current position of the celestial objects you can use one of the free sky maps available on the internet. I personally found the best to be Microsoft WorldWide Telescope. You can set your city position as well as go back and forward to a certain date in sky to observe the sky as it was at that date.