Astrophotography - Capturing Stars using a Telescope
Photographing the heavens and heavenly objects – astrophotography – is slowly gaining popularity, with the availability of a multitude of high resolution cameras and telescopes. This article takes you through the basics of astrophotography – how to go about photographing the stars using a telescope and your camera.
The Equipment Required
A. The Camera
You can either choose a point and shoot or an SLR. Needless to say, a P&S would give afocal photos as the lens of the camera would have to be held close to the eyepiece of the telescope. Valuable light is lost as the two surfaces are not in perfect opposition to each other. But with a little effort, one can get above average photos this way.
If you use an SLR (or a dSLR), removing the lens would allow the telescope to be fitted on to the camera, thereby directly projecting the image on to the film or the CCD, giving a sharper and superior quality image.
B. The Telescope
Your choice of telescope would determine what you would be able to shoot. A reflector telescope is usually better at shooting deep space objects like stars and galaxies, whereas a refractor telescope is better suited for objects closer to Earth, like the moon and planets. Major factors influencing choice of telescope is our requirements and often, our budget.
C. Attaching the telescope to the camera
The next step is getting your telescope to act as a lens for your camera. For this, you’d need to purchase a ‘T-Adaptor’, which fits in place of the eyepiece of your telescope, and a ‘T-mount’, which replaces the lens of your SLR. The T-adaptor fits quite snugly into the T-mount.
D. A Telescope Mount
The most critical component of your setup has to be the Telescope Mount. Its OK to even cut a few bucks off your telescope budget and invest it instead in a good mount. A mount is responsible for (a) sturdily holding the telescope (b) preventing vibrations (c) tracking the motion of the stars/planets so that you get a sharp image and not a ‘star trail’. There are three standard types of mounts available - the Altazimuth Mount, the Dobsonian Mount and the Equatorial Mount.
- The Altazimuth is the cheapest of the mounts and is similar to a tripod. It offers adjustment along the horizontal and vertical axes, but one is often limited to exposures of less than 30 seconds to compensate for star trails.
- A Dobsonian mount is similar to the altazimuth, but has a cradle and base kind of build, which offers smoother movement and easier handling. It can also bear more weight and is useful for larger scopes. Usually Dobsonian mounts come specific for a particular make of telescope.
- The Equatorial Mount is the most complex and most precise of telescope mounts. It’s a bit complicated to set up, and has to be accurately adjusted along the Earth’s Polar Axis. But once this step is accomplished, it’s a breeze to track star and planet movements. Its particularly useful in long exposures where the motion of the heavenly object needs to be tracked for extended periods of time. The more advanced models come with a motor and computerized panels which will automatically ‘Go To’ the specified coordinate of the skies.
Though the type of mount you buy would ultimately depend on your budget, its important to mention that choosing the right mount is essential for getting good photos of the stars.
Unlike what many may think initially, astrophotography is not one of the subjects you can easily learn by trial and error. It requires some amount of knowledge of the skies and of basic astronomy to be able to spot and recognize stars amongst the millions of shimmering spots in the night sky. It would be worthwhile to invest in a good astronomy book and take it to the field with you. I cannot emphasize more the importance of prior knowledge of basic astronomy in getting good photos of the night skies.
You’re pretty much set once you have the above in your possession. Now all you need is a dark, clear sky, preferably away from the city, lots of time and willingness to try and keep trying till you get images you’re proud of.