The camera obscura

Photographic cameras were a development of the camera obscura, a device dating back to the ancient Chinese[1] and ancient Greeks,[2][3] which uses a pinhole or lens to project an image of the scene outside upside-down onto a viewing surface. Scientist-monk Roger Bacon also studied this matter. Bacon's notes and drawings, published as Perspectiva in 1267, are partly clouded with theological material describing how the Devil can insinuate himself through the pinhole by magic,[4] and it is not clear whether or not he produced such a device. On 24 January 1544 mathematician and instrument maker Reiners Gemma Frisius of Leuven University used one to watch a solar eclipse, publishing a diagram of his method in De Radio Astronimica et Geometrico in the following year.[5] In 1558 Giovanni Batista della Porta was the first to recommend the method as an aid to drawing.[6] Before the invention of photographic processes there was no way to preserve the images produced by these cameras apart from manually tracing them. The earliest cameras were room-sized, with space for one or more people inside; these gradually evolved into more and more compact models such as that by Niepce's time portable handheld cameras suitable for photography were readily available. The first camera that was small and portable enough to be practical for photography was built by Johann Zahn in 1685, though it would be almost 150 years before such an application was possible. Roger Bacon, O.F.M. (c. 1214Ц1294) (scholastic accolade Doctor Mirabilis, meaning "wonderful teacher"), was an English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empirical methods. He is sometimes credited, mainly starting in the 19th century, as one of the earliest European advocates of the modern scientific method inspired by the works of Aristotle and later Arabic works, such as the works of Muslim scientist Alhazen.[2] However, more recent reevaluations emphasize that he was essentially a medieval thinker, with much of his "experimental" knowledge obtained from books, in the scholastic tradition.[3] A survey of the reception of Bacon's work over centuries found that it often reflects the concerns and controversies central to

the receivers. As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks ("occults") the Sun. This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses only part of the Sun is obscured. If the Moon were in a circular orbit close enough to the Earth and in the same orbital plane, there would be total solar eclipses every single month. However, the Moon's orbit is inclined or tilted at more than 5 degrees to Earth's orbit around the Sun (see ecliptic) so its shadow at new moon usually misses Earth. Earth's orbit is called the ecliptic plane as the Moon's orbit must cross this plane in order for an eclipse (both solar as well as lunar) to occur. In addition, the Moon's actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun totally. The orbital planes cross each year at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses.[1][2] However, total solar eclipses are rare at any particular location because totality exists only along a narrow path on Earth's surface traced by the Moon's shadow or umbra. An eclipse is a natural phenomenon. Nevertheless, in some ancient and modern cultures, solar eclipses have been attributed to supernatural causes or regarded as bad omens. A total solar eclipse can be frightening to people who are unaware of its astronomical explanation, as the Sun seems to disappear during the day and the sky darkens in a matter of minutes. Because it is dangerous to look directly at the Sun, observers should use special eye protection or indirect viewing techniques when viewing a partial eclipse, or the partial phases of a total eclipse. It is safe to view the total phase of a total solar eclipse with the unaided eye and without protection, however. People referred to as eclipse chasers or umbraphiles will travel to remote locations to observe or witness predicted central solar eclipses.