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The Planets
The planets are one of the first targets for every beginner amateur astronomer. Indeed, we get to see our own every day, but five others, Mercury, Venus, Mars, Jupiter and Saturn, could be easily seen with naked eyes. Technically, Uranus could be also seen with naked eyes, since it's just below 6-th magnitude - the limiting magnitude for most of us. These are among the brightest objects on the sky, so they are not hard to find.
Conjugations and sceneries
Using a camera with a regular focal length lens (around 50 mm), mounted on a tripod, could be very useful to capture the scenery plus some stars around the planet (see photo above). Also, such setup could be very handy during planet conjugations.
Close-up views
If you want to see or capture more of the planet of your interest, you would need a telescope. A telescope plus, probably, some additional magnification of your system is likely to be required. The different types of optical magnifications (Barlow lens, eyepiece, etc.) will be discussed in different section. No matter what kind of optical system and detector you are using, you have to know how big your target would be in your images (in the focal plane). To calculate that use this simple equation:
d = a x F / 206,265
where d is the size of the planet in mm, a is the angular diameter of the planet in arc sec and F the effective focal length of your optical system in mm. You can find the current angular size of the target planet in an almanac, online or using some planetarium software.
Equipment
Using a camera with a regular focal length lens (around 50 mm), mounted on a tripod, could be very useful to capture the scenery plus some stars around the planet (see photo above). Also, such setup could be very handy during planet conjugations.
Close-up views
If you want to see or capture more of the planet of your interest, you would need a telescope. A telescope plus, probably, some additional magnification of your system is likely to be required. The different types of optical magnifications (Barlow lens, eyepiece, etc.) will be discussed in different section. No matter what kind of optical system and detector you are using, you have to know how big your target would be in your images (in the focal plane). To calculate that use this simple equation:
d = a x F / 206,265
where d is the size of the planet in mm, a is the angular diameter of the planet in arc sec and F the effective focal length of your optical system in mm. You can find the current angular size of the target planet in an almanac, online or using some planetarium software.
Equipment
| Getting an image of a planet through a telescope, especially when using some sort of optical magnification, could be tricky and hard to get. For a start you would need a decent size telescope - at least 6" (150 mm), and a sturdy motor driven mount. Not that is impossible to use a telescope with diameter less than 6" (see my Saturn example below). If that's what you have go for it; you could definitely get some decent images. However, some of the nice details would be lost due to poor resolution. In addition, your system would lack light collecting power, thus requiring longer exposure times leading to fuzzier images (lost details), because of turbulence, vibrations, etc.
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After you have settled on an optical system, decide what kind of detector you would use. You have three general choices here - CCD, web or a regular camera. The best results could be achieved by a web camera. If you don't have one, use what you already have. There is a separate page discussing in a greater details these three detectors. Here, I'll just give you a brief overview.
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- CCD cameras. With such cameras you would need to get at least three frames in different filters to get a color image. In general, that wouldn't be my first choice.
- Web cameras. They have proven themselves to be the best choice for planetary photography. Granted, you would need a software to process and "stack" your frames to get an image, but is definitely worth it.
- Regular cameras. These could be two types:
- Film cameras. Depending on your magnification, thus required exposure time, stick within the 100-400 ISO range. For all my photos I seldom had to take exposures more than 10 sec. The shorter your exposure time the better.
- Digital cameras. ISO range similar to the film cameras, but please do experiment to find what would fit you best. Digital cameras do a better job in "collecting" photons.
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Other essentials that you may need to have can be found on the Observing tips page.
About the photos on this page
Top. This is a photo of the twilight plus Venus, taken with a 50 mm lens and a film camera (ISO 200), several seconds exposure time.
Mars. Taken with a Celestron C8, D = 203 mm, effective focal length F ~ 10,000 mm, film camera ISO 200, 5 sec exposure time.
Jupiter. Taken with a Maksutov-Cassegrain telescope D = 150 mm, effective focal length F ~ 22,500 mm, ISO 100, 6 sec exposure time.
Saturn left. Taken with a Maksutov-Cassegrain telescope D = 150 mm, effective focal length F ~ 22,500 mm, ISO 100, 12 sec exposure time.
Saturn right. Taken with D = 63 mm (less than 2.5 inches!!!), F = 840 mm, digital point-and-shoot camera (but a decent one) attached after the eyepiece. Effective focal length F ~ 2,000 mm, exposure time 1/13 sec, ISO 100. Keep in mind that the crop factor would be very different from a regular film camera or even a DSLR.
Digital vs. film cameras
My Saturn experiments (see pictures above) are in favor of the digital cameras. As you can see, with proper settings you could get better images with a 2.5" (2.48" if we have to be precise) telescope than a 6" one. You should realize that the actual resultant size, in mm, of the planet in the focal plane of my system is much larger in the film camera setup. However, the biggest problem is the long exposure time of 12 sec (vs. 1/13 sec in the digital setup). This allows turbulence, vibrations and imperfection in the guiding system to smudge the image, "robbing" of its resolution.
As a conclusion, aim for no more than several seconds exposure times and play with your magnification system to get optimal, for your telescope, results.
About the photos on this page
Top. This is a photo of the twilight plus Venus, taken with a 50 mm lens and a film camera (ISO 200), several seconds exposure time.
Mars. Taken with a Celestron C8, D = 203 mm, effective focal length F ~ 10,000 mm, film camera ISO 200, 5 sec exposure time.
Jupiter. Taken with a Maksutov-Cassegrain telescope D = 150 mm, effective focal length F ~ 22,500 mm, ISO 100, 6 sec exposure time.
Saturn left. Taken with a Maksutov-Cassegrain telescope D = 150 mm, effective focal length F ~ 22,500 mm, ISO 100, 12 sec exposure time.
Saturn right. Taken with D = 63 mm (less than 2.5 inches!!!), F = 840 mm, digital point-and-shoot camera (but a decent one) attached after the eyepiece. Effective focal length F ~ 2,000 mm, exposure time 1/13 sec, ISO 100. Keep in mind that the crop factor would be very different from a regular film camera or even a DSLR.
Digital vs. film cameras
My Saturn experiments (see pictures above) are in favor of the digital cameras. As you can see, with proper settings you could get better images with a 2.5" (2.48" if we have to be precise) telescope than a 6" one. You should realize that the actual resultant size, in mm, of the planet in the focal plane of my system is much larger in the film camera setup. However, the biggest problem is the long exposure time of 12 sec (vs. 1/13 sec in the digital setup). This allows turbulence, vibrations and imperfection in the guiding system to smudge the image, "robbing" of its resolution.
As a conclusion, aim for no more than several seconds exposure times and play with your magnification system to get optimal, for your telescope, results.
