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How to Photograph the Sun
When it comes to photographing the Sun, you have probably seen various photos of the Sun, in all of which it has different colors. There is no mystery about it, it all depends on the filter you have, and a filter you must use. Well, unless you are taking scenic pictures during sunrise/sunset.
The most obvious thing that you would want to see on your pictures are the sunspots. They vary in sizes and numbers. When you photograph the Sun during different time of the 11 year solar cycle, could be quite different. During maximum solar activity, the Sun could be covered in sunspots, many of which large enough, and worthy of your interest. On the other hand, during minimum, you may not find even a single sunspot. Photographs are probably the most unbiased method of calculating the Wolf number. For more information about sunspots, groups and Wolf number calculation, see How to draw the Sun section.
What kind of lenses/telescopes to use?
When you photograph the Sun, you are rarely concern about the aperture of your instrument. Let’s face it, the target you are interested in is quite bright, and you don't really care about collecting power. Granted, the aperture affects the resolution, but any decent size instrument will do. So, what you would mainly care about is the focal length of your telescope, and here is why:
When you photograph the Sun, you are rarely concern about the aperture of your instrument. Let’s face it, the target you are interested in is quite bright, and you don't really care about collecting power. Granted, the aperture affects the resolution, but any decent size instrument will do. So, what you would mainly care about is the focal length of your telescope, and here is why:
The image above shows how the Sun would look like in your camera with different focal lengths. As you can see, to have a decent shot of the sunspots you would need to use at least a 500 mm (or even a 1000 mm) lens. Keep in mind that these images are for a 35 mm film camera. When using a digital one, the relative size of the Sun would depend on the size of the camera chip. Most 2:3 DSLR (Digital Single Lens Reflex) cameras have slightly smaller chip size, so to get the 35 mm focal length equivalent you would have to multiply roughly by 1.6. For 4:3 DSLRs you would have to multiply by 2. With full frame DSLRs, which sensors have the same size as 35 mm film camera (36 x 24 mm), you don't need any conversion. Remember that the absolute size of the Sun in mm will always be the same, no matter what camera you are using!!!
To photograph the Sun you would often use additional magnification to capture only a group of sunspots or a very large one. There would be a separate section about Barlow lenses, eyepiece magnification, etc.
After you know what your optical system and your final focal length would be, you can calculate the Sun's size in mm using this simple equation:
d = 0.0093 x F
where d is the size of the Sun in mm and F is the focal length of your instrument in mm. Knowing the resultant size in mm and the size of your detector, you could determine how big the Sun would look like, or what fraction of it would be on your photographs.
To photograph the Sun you would often use additional magnification to capture only a group of sunspots or a very large one. There would be a separate section about Barlow lenses, eyepiece magnification, etc.
After you know what your optical system and your final focal length would be, you can calculate the Sun's size in mm using this simple equation:
d = 0.0093 x F
where d is the size of the Sun in mm and F is the focal length of your instrument in mm. Knowing the resultant size in mm and the size of your detector, you could determine how big the Sun would look like, or what fraction of it would be on your photographs.
