This book is about how to take, and process, planetary images with a DSLR camera. It describes the theory and practice of planetary photography and how to best use telescopes and DSLR camera hardware, image-capture software, and planetary image-processing software. Its purpose is to educate the reader and help him or her learn how to take satisfying planetary images and get the best out of their own personal equipment. Its intended audience is amateur astronomers who have a telescope and a DSLR camera and are interested in learning or improving their planetary-imaging skills. This book describes taking images mostly with Canon DSLR cameras and special software has been developed that records Live View video and makes high-resolution planetary imaging possible. At this writing, only one program will record Nikon Live View and that with only the latest Nikon models. Previous Nikon models had limitations that made them unsuitable for planetary photography. Other manufacturer's cameras may be usable for planetary photography, but no one had written any software to record Live View with these cameras at this time. Planetary Photography Planetary photography encompasses the Sun, Moon, major and minor planets, as well as satellites, meteors and comets. Basically, it is anything outside of the Earth's atmosphere, but inside of the solar system. To take images that show details on planets such as Mars and Jupiter, we will need to do high-resolution, high-magnification work. But for larger objects like the Moon, there are plenty of details to record with much simpler techniques. Indeed, some incredibly beautiful wide-field planetary images can be taken with just a camera, wide-angle lens, and a tripod. Very brief and basic overviews for each of the three main parts of planetary photography are provided here: Planetary Photography Through the Years For more than 150 years after photography was invented, astrophotographers used film. The results they got for faint deep-sky objects were revolutionary because film emulsions could record more than eye could see. A whole new universe was literally discovered with the results from film astrophotography. The story was different for high-resolution planetary photography however. Rarely were astronomers able to photograph detail as fine as they could see visually. They were limited by the turbulence in the Earth's atmosphere called seeing and the resolution and sensitivity of the film they were using. They were able to catch very brief moments of good seeing visually, but the long exposures required by film would blur these moments in a photo. The trouble with visual observing is that it involved the mind and consciousness. Some incredible observations were made, such as of Encke's division, a 325 kilometer gap in the outside of the A ring of Saturn, by James Edward Keeler in 1888 (Encke never actually saw the division curiously named after him). But other unreliable observations were also claimed, such as those of the famous canals on Mars by Percival Lowell which did not, in fact, exist. The Digital Revolution In the late decades of the last millennium, digital photography began with the invention of the charge-coupled device (CCD) in 1969 at AT&T Bell Labs by Willard Boyle and George E. Smith. To the delight of scientists and astrophotographers, digital sensors revolutionized both long-exposure deep-sky astrophotography as well as high-resolution planetary photography. As digital sensors became a commodity, they spread into all kinds of devices, such as cell phones and web cameras. Astrophotographers were inspired to try web cams in their telescopes and to use "lucky imaging" on the planets with these video cameras. The results were amazing. Amateurs were now taking some of the best planetary images, rivaling professional observatories. DSLRs for Planetary Photography DSLR cameras offering Live View and high-definition video recording capabilities can be used with lucky imaging for high-resolution planetary photography. In this book, you will learn about: Planetary photography is all about these things, and each is critically important: You can have a lot of fun using a DSLR for planetary photography and long-exposure deep-sky astrophotography, and you have the added versatility of being able to use the DSLR for daytime shots of your family and friends. A Little History High-resolution planetary imaging is about capturing detail during brief moments of good seeing. In the old days of film photography, this meant shooting as many frames as you could, and hoping that one would be sharper than the others. Shooting a lot of frames, however, got very tedious very quickly. You would have to mechanically advance the film after every exposure, and then wait for that disturbance to die down before you could take the next frame at high magnification. Even the shutter opening could blur an image.
Astrophotographers invented the "hat trick" to solve this problem. A hat would literally be held in front of a small aperture telescope, the shutter opened, and when the vibrations died down, the hat would be removed for somewhere between 1/2 second to several seconds, depending on how long an exposure was needed. A larger opaque piece of cardboard was used for larger apertures. Needless to say, the accuracy and repeatability of short exposures with this method was less than perfect. Film astrophotographers could really only take about one frame every 5 to 10 seconds and could not get a really large number of frames before they either ran out of film or the planet rotated too much. It was very expensive in terms of film and developing costs. It also took time to get back the results to see if a night's imaging session was successful. Today's digital cameras have no film or development costs and images can be viewed immediately after they are shot. There were some amazing films in the past, like Kodak's now-discontinued 2415 Technical Pan film. "Tech-pan", as it was called, had amazing resolution compared to other films. But it was not that sensitive to light, so we had to shoot longer exposures, and those brief moments of good seeing usually ended up getting blurred and lost in the longer periods of bad seeing during a single exposure. It was the longer exposures required by the low sensitivity of film that really killed the chance to record exceptionally high-resolution detail, even if there were moments of great seeing.
It's not that there weren't some good planetary images taken in the days of film. There certainly were. The problem was that, unlike long-exposure deep-sky images that recorded more than could be seen visually, planetary observers could still see more detail visually than they could record on film. These subjective observations, however, led to erroneous claims such as those of the canals of Mars by Percival Lowell. Today, digital cameras with lucky imaging can objectively record more planetary detail with video than can be seen visually.
Video is a descendant of film motion pictures, and electronic and solid state television cameras. Motion pictures were invented in the late 19th century, shortly after the invention of photography itself. In reality, motion pictures are nothing more than a series of still images shot in rapid sequence. When they are played back in rapid sequence, the human visual system's persistence of vision fools the mind into thinking that the motion is smooth and continuous, if the framing rate is fast enough. Electronic video cameras were invented in the 1900s and used in recording television programs by mid-century. Solid state CCD (Charge-Coupled Device) digital sensors were invented in 1969. CCD and CMOS (Complementary Metal Oxide Semiconductor) sensors became ubiquitous in all kinds of devices towards the end of the century. Today, in the 21st century, these sensors are used in video cameras, web cams, dedicated astronomical imaging cameras, snapshot digital cameras, phones, computers, and DSLR cameras. The latest generation of DSLR cameras can also shoot video. This opens up many possibilities for digital high-resolution planetary imaging with DSLRs. With video, instead of a series of images being recorded on film, they are recorded with electronic sensors that digitize the information. Digital cameras can easily out-resolve film when used with lucky imaging for planetary photography. Miscellaneous Notes Images in this book are presented, for the most part, with south up, which is the tradition in planetary photography. This is a holdover from the days of visual drawings of the planets which were usually inverted because a refractor was used. This is the opposite of deepsky photography which usually presents north up. Note that this is just a tradition, and not a law! Some of the images in this book have north up. Just call me a renegade. The terms "movie" and "video" are used interchangeably in this book. Movies were originally made as a series of still images on long lengths of film where each image was called a frame. Videos are a series of electronic still images that were originally stored on magnetic tape. Today, both movies and videos are made with digital cameras, and both are a series of still images that when played back rapidly enough, fool the eye into thinking it is continuous motion. |
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