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Last week, we looked at how to photograph the night sky using just a camera. We had looked at photographing star trails and meteor showers. This week, we will answer the question of how to begin to learn to photograph the objects in the sky.
The easiest way to begin to learn astrophotography is without a telescope. Using a telephoto lens, begin taking higher magnification photographs of star fields, the sky above the horizon, and the Moon. This can be achieved quite well with a lens having a focal length of around 105 mm. Doing this will get you used to the smaller fields of view available at longer focal lengths, and will help develop a sense of what will be seen through a camera equipped telescope.
For most astrophotography applications, the image seen through the camera viewfinder is of a much lower magnification than most eyepieces deliver without a camera. Even the terminology used to express the degree of magnification is different. When talking about the magnification of a telescope, a common figure is 115X. This means the object you are looking at appears as if if were 115 times closer to you. The Moon, for instance, which is about 230,000 miles away, would appear as if it were only 230,000/115, or 2000 miles away. Only the distance from New England to Florida!
When looking through a camera equipped telescope, however, the magnification is expressed as a certain number times the magnification seen through a 50 mm lens. Why this is, is quite simple to explain. Imagine looking through a plain 35 mm camera with nothing but a normal 50 mm lens. If you are not used to photography, and cannot picture it, try it! The image seen is not what the human eye sees normally. Thus, the view seen through a camera attached to a telescope has to be expressed as a ratio of fields of view. If you were to attach a camera to a telescope which had a focal length of 1000 mm, the magnification would be 1000/50, or 20 times the magnification seen through a 50 mm lens.
In order to physically attach the camera to the telescope in the most common manner, you must have two parts. These are known as a t-adaptor and a t-ring. T-adaptors are made to fit on a telescope, and t-rings attach to the camera. Because of this, you need to purchase a t-adaptor for your brand of telescope, and a t-ring for your brand of camera. Each of these pieces costs between $20 and $50 in most cases. Simply attach the t-adaptor to the telescope, and then attach the t-ring to the camera, connect the t-ring to the t-adaptor, and you are well on your way to astrophotography.
You can photograph the Moon, and all the brighter planets without a motor drive. Try the Moon first, then the brighter planets, Venus, Jupiter, and Saturn. Only if you decide to invest in a motor drive for your telescope should you attempt nebulae and galaxies. When you do, start out with the easier ones such as the Orion Nebula, the Pleiades, and M31.
It is best to develop your own film (as we discussed last week, make sure to use a high speed film, ASA 400 or higher), but if you cannot do that, make sure to request that the photo shop developing your precious film does NOT cut the negative, and be sure to ask that they print every frame. Too many good astrophotos are lost due to a poor cut, but a photo shop; after all, finds it difficult to tell where astronomical photos begin and end on a negative. Many astronomical photos look to the people working at photo stores like errors, and they do not print them. They see only a small dot on a negative, and assume that was not what the picture was of. But you spent a good part of an evening trying to photograph that dot! The few extra cents per poor quality frame is well worth the joy of getting one good one which may otherwise have been lost.
Clear skies, and good viewing.
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