The art of astrophotography is an activity that many have engaged in without even realizing it. Anyone who has stood outside on a clear night and snapped a picture of a full moon or taken a picture of the stars is an astrophotographer. In its most simple terms, astrophotography is the documenting of the night sky through photographs. This can be as simple as an average citizen with a cell phone camera to as complex as the NASA complex taking pictures from a satellite.
Astrophotography got its beginning in 1840 when the very first picture of the Moon was taken. Since then it has advanced and changed immensely but it was not until the late 19th century that technology had advanced enough to get some truly spectacular images. In current times, it is now possible to not just take a picture of the Moon but to take detailed photographs of celestial bodies that are beyond the reach of humans and can only be viewed with modern technology, like distant planets or nebulas.
Professional astrophotography exclusively employs the use of long exposure times in order to capture such detailed images. Since many of these celestial bodies are dim or invisible to the naked eye on Earth, the film must be exposed to the area for a longer period of time. By increasing the amount of time the film is exposed, that will increase the amount of light and detail that photograph is given. Because of the issues of light pollution, most professional astrophotographers work far away from cities so that they can maintain such long exposures without the film being ruined by ambient light. Another complicating factor is that the Earth is constantly rotating, which would make the photographs blurry if the camera or telescope was made stationary. For that reason, the camera or telescope is programmed to rotate in the opposite direction and follow the "movement" of the item being photographed. This is all very complicated and can be accomplished by only the most advanced and professional astrophotographers, but the amateur can still get superb pictures without all of these complicated calculations. There is even some amateur equipment on the market that allows for tracking to combat the rotation of the Earth and increase picture clarity.
There are many techniques for the amateur astrophotography and each comes with it's own challenges and equipments needs. Many beginners like to start with the most simple of techniques and then graduate up to more complex setups as they gain more experience. Some of these techniques include:
- Fixed/tripod mounts. The most common setup for astrophotographers is a tripod set up. In this method a standard camera and photographic lenses are fixed onto a tripod mount so that the field of the camera remains constant. Because this is standard equipment that also means that sometimes other objects appear in these photographs like trees or mountains. The most commonly photographed objects with this setup are bright celestial bodies that are easily viewed with the naked eye like bright stars, constellations or a comet. Exposure time with a fixed mount must be less than a minute or else the stars will star to blur because of the Earth's rotation. For that reason, more dim objects cannot be photographed since they would require a longer exposure time. Lens focal lengths are also kept short since longer lengths can lead to blurring of the image in a much shorter time. Sometimes images are intentionally blurred to achieve the "star trail" effect for artistic purposes but for most it is avoided.
- Tracking mounting. This is a more advanced kind of astrophotography. In this method, the photographer is using a tracking systetm so that they can maintain longer exposure without blurring the image. Some tracking systems are homemade and others are available commercially. For this reason, the method of tracking will vary widely based on the individual photographers. All of them use a single point in the sky (usually a bright star) as a reference point and keep the camera trained on that star as it moves across the sky. This means that the field of exposure remains the same and a clear image is produced.
- "Piggyback." This method of astrophotography is a very general term for a specific kind of setup. This is when the photographers mounts a camera to a telescope that has equatorial tracking on it. This means that the telescope acts as a tracking mount so that the camera moves along with the telescope and allows for a long exposure time.
- Telescope focal plane. While the name may be complicated this method is quite straightforward. This means that the telescope itself is used as a lens to take the photographs. This is the most difficult kind of astrophotography and requires a large amount of equipment and experience. The telescope can be used as a focus for the camera lens and expose the film directly with what the telescope sees. The biggest benefit of using this technique is that the magnifying power of the telescope can be used to get photographs that are of much dimmer objects, and so the photographs can be much more spectacular.
Astrophotography is a quickly growing hobby and new methods of getting involved in it are being developed all the time. It can be as expensive or affordable as the photographer wishes to make it and can be as easy or complex as they wish. Humankind has been fascinated by the stars for as long as we have existed. This fascination is apparent in astrophotographers and all those who are intrigued with the images they take. This field of interest is not likely to go away any time soon but only to increase as new methods make it even easier to reach further beyond humanity's grasp.