Astrophotography a.k.a celestial photography, astronomical imaging, night-sky photography is both a challenging and yet rewarding "unique" form of photography. It is unique in that astroimagers must capture a properly exposed and technically sharp image of a celestial subject that is a point of light in the night sky. These astronomical subjects such as planets, stars, galaxies, etc., are billions of miles and often light years away!
Imagine trying to successfully capture such an object during night-time conditions when the lighting is extremely low. Night-sky photography is no doubt the toughest test on your optics. Astrophotography involves shooting long exposures in extreme low-light conditions on a point of light source. Below are some tips and techniques to help you get started in this exciting and rapidly-growing field:
1. Use a standard 35mm DSLR camera on a sturdy tripod to start out.
2. Be sure to use a remote (electronic) shutter release (in order to eliminate camera movement).
3. Be sure that your camera has a Bulb or "B" mode as well as Tv, Av and M modes.
4. Be sure to use fast lenses a.k.a. as "fast glass". The best lenses are "prime" lenses where each lenses focal length and widest-open aperture is constant. For example, a 50mm f1.2, f1.4. f1.8 and f2.0 are fast prime lenses. The more wide open the "aperture" (lens opening" the more light (photons) can be absorbed by the camera's sensor (chip). In astroimaging, everything is about "more photons".
5. Wide-field lenses such as 50mm and less will be great for wide-field astrophotography which is great for earth and sky photography, constellations, meteors, comets, auroras, the moon with a landscape, planetary conjunctions, etc. Again, prime lenses are better because they are usually faster, sharper and are cheaper in cost.
6. If you want to get into more magnification on your subject then prime lenses beyond 50mm are a good choice. These lenses will not only be great for landscape photography but also when you want to zoom in on the moon, galaxies, nebulaes, comets and earth & sky captures. Again, use "fast primes".
7. Do you best to image from a dark-sky location where there is little or no light pollution. The darker your sky, the longer your exposures and the more celestial objects your sensor can capture. Dark-sky sites also make it easier to visualize the beautiful night sky especially the milky way, comets, auroras and meteor showers.
8. Start out with the basic form of astro imaging which is camera on tripod that is untracked. A good start on settings is f2.8 or lower for your aperture and keep your exposure times no more then 25 seconds. The "500" rule is a good guide to help you determine correct exposure times when using your focal length lenses. This rule says to divide your lenses' focal length into 500 and this number will be the maximum number of seconds that you can expose for. For example, a 50mm lens: divide 500 by 50 and you get a maximum exposure time of 10 seconds. Any exposure of a star field past 10 seconds will run the risk of capturing star trails. The more wider angle the lens, the longer the exposure can be before trailing occurs.
9. Start out with untracked exposures and use the 500 rule. Tracking and guiding takes you into the deeper end of the pool.
10. Make your first photoshoot be the Moon. Our moon is big and bright and has lots of detail in relief along its terminator line which is best seen and captured on half phase. With the moon being bright, you will also be able to use your camera's shutter priority mode (Tv or S) since more light will allow for exposure times in fractions of a second. You would need at least a 400mm lens minimum but 500 and 600 is even better to fill your camera's viewfinder and capture those wonderful lunar details.
11. One of the best times to capture a full moon is when it is rising in the east along a flat horizon. Look for the "moon illusion" when the moon appears extremely large due to our earth's thicker atmosphere along the horizon.
12. Be sure to make it a habitat to clean the front and rear optical elements of each of your lenses before you put them on your camera.
Enjoy the night sky!