2
Astrophotography
Astrophotography is more popular today than it has ever been. Electronic imaging has
revolutionized the field and high quality digital single lens reflex (DSLR) cameras and charged
couple devices (CCD) and are within the price range of many amateur astronomers. With the
high sensitivity and linear response of these cameras, amateur astronomers are now capable of
producing images from their back yards that only a few years ago would have rivaled those
produced by professional astronomers at the world‟s best observatories. However,
astrophotography is unlike all other types of photography. With standard photography, there is
ample light to permit bright imaging of the subject in the wink of an eye. Exposures may be a
fraction of a second, perhaps thousandths of a second. Despite these incredibly short exposures,
each pixel in the camera generally records thousands of photons that comprise the image. Every
possible brightness level within the dynamic range of the camera is loaded with ample data.
Not so with astrophotography. Because the subjects of astrophotography, such as star clusters,
nebulae, and distant galaxies, are inherently dim, all astrophotography requires time exposures of
considerable length to capture enough photons to have a chance at making the subject visible.
Exposures range from minutes to hours. Even then, most pixels in the camera register almost no
photons or barely a few more photons than the background noise that builds up in the pixels or
the background sky brightness during the exposure. The amount of data captured is actually quite
small and is confined to a very narrow range of brightness within the darkest shadow region of
the camera‟s dynamic range.
The art of astrophotography comes with the image processing. The trick is to take that data
confined to such a narrow range and skillfully stretch it through a much wider dynamic range,
similar to that used in daylight photography, so that we perceive the illusion of viewing a bright
scene. However, it is an illusion. Were we actually there, as close to a nebula or galaxy as the
telescope view makes it seem, our eyes would actually see almost nothing. Thus, it is the
combination of the magnification and light gathering power of the telescope, the integration of
time exposures to capture as many photons as possible, and the power of image processing that
make astrophotography the miracle that it is. We can image that which cannot be seen. No
wonder it is so rewarding to those who pursue it.
The Celestron Compustar Telescopes
The Celestron Compustar telescopes were the first computer controlled “Go-To” telescopes.
They premiered in 1987, a full 5 years before the Meade LX200 series that most people
remember as the first mass-produced Go-To telescopes. As the story goes, Celestron contacted
computer engineer Mike Simmons and his company, ATI, to help them produce a new line of
robotic telescopes. What Mr. Simmons and ATI did, by connecting the relatively simple (by
today‟s standards) computers of the day with a Schmidt-Cassegrain telescope with the use of
stepper motors to move the mount, was amazing. The results were the Compustars, telescopes
(66 Seiten)
(80 Seiten)
(68 Seiten)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Kommentare zu diesen Handbüchern