摘要: Description　　It is well known that Astronomy in Egypt started a long time ago, and Egypt is considered as one of the oldest countries whose people studied astronomy. The Egyptian monuments at Nabta Pl

Description

　　It is well known that Astronomy in Egypt started a long time ago, and Egypt is considered as one of the oldest countries whose people studied astronomy. The Egyptian monuments at Nabta Playa (Neolithic, which antedates Stonehenge by a millennium), the Pyramids at Giza (4^th Dynasty), Abu Simbel Temple (21^st Dynasty) and the zodiac at the Temple of Denderah (Ptolemaic), all bear distinct evidence that Egyptians were very much preoccupied with observing heavenly bodies and their motion, with unrivalled skill.

　　The Alexandria school (330 BC -168 AD) attracted famous scientists to come to Egypt, where the circumference of the Earth was measured for the first time by Eratosthenes from his observations in Aswan, and the famous Almagest (The Great Compilation), a mathematical and astronomical treatise proposing the complex motions of the stars and planetary paths, was written in the 2nd century AD by Ptolemy of Alexandria, which remained valid till the 16^th century.

　　During the Arab period, astronomical sciences continued to advance in Egypt by observing many stars and Nebulae (although Nebulae were discovered in the 20th century, some were earlier observed by the Arabs). Nowadays, most of the star names are of Arabic origin, like Aljabir, Altair, Aldabaran. Furthermore, some astronomical instruments like the astrolabe were efficiently used by Arab navigators. The Arabs, under Fatimid rule, erected many observatories in Egypt, such as at the Moqattam Hills east of Cairo (11 th century AD), notably EI-Guyushy and the EI-Maamoon Observatories. IbnYunus wrote in that period an accurate astronomical table known as al-Zi} al-Kabir alHakimi (Big Hakimi Zij), and also wrote the Kitab bulugh al-umniyya (liOn the Attainment of Desire"), a work concerning the heliacal risings of Sirius, and on predictions concerning what day of the week the Christian Coptic year will start on. His works are noted for being ahead of their time, having been based on almost modern-like meticulous calculations and attention to detail. The crater Ibn Yunus on the Moon is named after him.

　　Modern Astronomy in Egypt

　　Modem Egyptian astronomy was revived and developed at the hands of the first modem notable Egyptian astronomer, Mahmoud Pacha EI-Falaki (1815-1885), who pioneered the Egyptian Renaissance in the mid 19th century. EI-Falaki (the astronomer) became his family name. In 1842, Mahmoud decided to study astronomy and practiced at the first modem Egyptian Observatory at the Boulaq Rassd-khana (Observatory), built in 1840. He was commissioned by Khedive Ismail to observe the solar eclipse in the 1860s, which made news in the country.

　　Another observatory was built in 1865 at Abbasiya, NE of Cairo (Fig. 1), at his advice and supervision. It was later transferred to Helwan, south of Cairo, in 1903, due to urban encroachment. The Abbasiya Observatory, however, remained till 1952 standing as an empty monument. The Helwan Observatory was built on top of a limestone plateau (116 m a.s.I), on the eastern side of Helwan city. The observatory was provided by a 30 inch reflector telescope offered by M. Reynolds in 1905 (an English astronomer, who becamelaterthetreasurer ofthe Royal AstronomicalSociety ofthe UK).

　　The story of the 30 inch telescope at Helwan

　　The historical 30 inch Reynolds's reflector at Helwan (Fig. 2) was the first large telescope inThe historical 30 inch Reynolds's reflector at Helwan (Fig. 2) was the first large telescope in Africa and the Middle East till 1945 and was the first telescope in the world to record Halley's Comet in 1909 and 1911. The finder telescope fitted to it was also used by Herschel to observe the Comet in 1835/6. - 3

　　The historical Observatory at Helwan also contains two Clock Rooms which have been used in the 18th century for time service and adjusting artificial satellite observations. An old 6 inch Zenith telescope has been used since 1874 for correcting the time recording by Meridian passage of stars. Two historical buildings of 1903, and many old astronomical instruments are still kept there.

　　Helwan Observatory in post-war period

　　Helwan Observatory was provided by a 74 inch reflector from Grubb Parsons

　　U.K. The Egyptian government ordered the telescope in 1948, the same year that the giant telescope of Mount Palomar, California was erected. Tracking Artificial Satellite telescopes and stations have been directly installed at Helwan Observatory after the launch of the first satellite in 1957. In the same year a horizontal solar telescope was erected to observe transient solar phenomena, and solar activity cycles. Different names have been given to the present Institute which was known as Helwan Khedivial Observatory in 1903, Royal Observatory in 1946, and finally became in 1986 the "National Research Institute of Astronomy and Geophysics (NRIAG)". NRIAG has two main scientific branches, namely, Astronomy and Geophysics. Each branch consists of several departments, laboratories and units.

　　Historical Observations at Helwan:

　　Observing Galaxies:

　　Since the Reynolds 30-inch reflector was first brought into regular use in Januaryl909, its chief work has been the photography of nebulae. This has been confined almost exclusively to those galaxies south of the Equator and includes nebulae down to 44 degree south declination, the southern limit of the telescope. Except in the case of a few nebulae which have been the subject of special study, such as the Variable Nebulae in Corona Australis, of which over 130 photographs have been taken, it was the aim of the work to obtain two photographs of each nebula from the 310 nebulae observed at Helwan till 1922. Table 1 gives the number of nebulae observed at Helwan in each zone from 0 to 45 degree south declination (Knox-Show 1922).

　　Table 1: Bright and Large Nebulae Observed at Helwan till 1922 (see Knox-Shaw 1924)

　　Zone

0°_

SO

10°_

ISO

20°

2So

30°

3So

40°

　　Total

　　South declination

So

10°

ISo

20°

2so

30°

3so

400

45 0

　　Total known

67

78

53

36

39

46

48

45

42

　　454

　　Photographed at Helwan

36

47

41

29

29

41

39

38

22

　　322

　　Not yet

26

31

12

7

9

5

9

7

20

　　126

　　~graphed

　　The modern galaxy classification

　　The Reynolds reflector helped the astronomical community in the development of the modem galaxy classification. The early systematic work of Knox-Shaw, Gregory, and Madwar with the Reynolds reflector at Helwan (Vols. 1 and 2 of He/wan Observatory Bulletins). Knox-Shaw (1915a) and Reynolds (1920) were among the first to call attention to amorphous galaxies with no trace of spiral arms, "E systems" (Sandage 1975).

　　Observing Comets:

　　The Reynolds reflector for a search of Halley's Comet during its visit to the earth in 1909 (Reynolds 1907, Knox-Shaw 1911). During 1909 photographs of Halley's Comet were obtained by Mr. Knox-Shaw on August 24, September 13, 15, and 16, October 15 and 22, and December 7 (Fig 3). Observations of the comet continued for 3 years till 1911, so there is a complete series of photographs for the entire period it was observable.

　　After the success of observing Halley's Comet, the telescope was utilized for the photography of comets -in order to determine their positions -which are either so faint or so situated as to make their observation with smaller telescopes or at more northerly observatories difficult. Comets like Neujmin, Grigg-Skjellerup, Forbes, Tempel's, Peltier Whipple, Kaho, Peltier, Jackson, Brook's, Wolf's, Borrelly's, Quenisset's, Beljawsky's and Mellish were regularly observed by the 30 inch Reynolds telescope (Madwar 1937, Curry, 1927, 1929,1930,1931,1933, Knox-Shaw 1912a, Knox-Shaw 1915b).

　　Observing The Eighth Satellite of Jupiter:

　　The search for Jupiter VIII was unsuccessful in 1921, but the satellite was found in 1922 February. Fifteen good plates were obtained for the satellite, and it's various positions were derived ( Knox-Shaw 1912b, Knox-Shaw 1916).

　　Discovery of Pluto :

　　The 30 inch telescope was used in 1930 to search for the planet Pluto according to the celestial position suggested by Persival Lowel (1915), in the publication Memoir on a Trans-Neptunian planet) from the deviations of orbital motions of the planets Uranus and Neptune with respect to theoretical results. According to Helwan observations the celestial position of Pluto was found to be deviated by 7 degrees from the location defined by Persival Lowel.

　　Observing the Solar Constant:

　　Helwan astronomers participated during (1914-1921) in the international programme of measuring fluctuations of the Solar Constant under the supervision of Professor Abott. Some of Helwan values (1367 Watt/m²) of the Solar Constant coincide with the results obtained by Rockets, Solar Max. Satellite and the Earth Radiation Budget Experiment (ERBE) Mission during 1980 and 1992 respectively (Eckersely 1914; Knox Shaw1915).

　　Observing: the Total Solar Eclipses:

　　Helwan astronomers took an active role in the observations of the total Solar Eclipse (1952) in Khartoum, Sudan, together with the famous French scientist Bernard Lyot. A wealth of information was obtained from the secured observations about the spectroscopic structure and physical conditions prevailing in the solar corona (Comptes Rendus Acd Sci, 237, 1955). Moreover, successful observations were registered by solar astronomers of Helwan for the 29 March 2006 total solar eclipse, observed at Salloum in the NW of Egypt. The data enabled to develop the processing methodology of digital photography and calculation accurate models for the magnetic structure of the Solar Corona.

　　National Services and Public Outreach:

　　In addition to its R&D functions, Helwan Observatory has provided, SInce establishment in 1903, the following national activities,

• Time service activities, which lasted up to 1961, the Meridian Circle telescope, erected in 1874, has been currently used to observe the meridian passage of stars and correct the time, which was broadcast to airports, harbours, radio and TV stations, and the clock of Cairo University.
• Synoptic observations of meteorological elements and weather forecasting in Egypt up to 1944.
• Housed the Standard Tools for Meteorology up to the Sixteenth.
• Organizing tours for the general public, pupils in schools, and students of universities to visit the Museum of Astronomy and Geophysics, to watch the moon and stars at night, and the Sun during daytime, using amateur telescopes.
• The Museum of Helwan observatory has a long history of activity. It was envisioned as an objective manifestation of the efforts made, in the course of the last centuries, to promote astronomical and geophysical cultures and studies in Egypt.
• Popularization of Astronomical and geophysical Sciences.

　　Thousands of visitors have visited this museum to see illustrating models of the celestial sphere, the mounting of Mahmoud Pasha EI-Falaki 10-inch refractor, models of seismographs and samples of successful astronomical photographs taken by the 30-inch telescope for Halley's comet, nebulae, planets, and moons. Furthermore the museum contains two Clock Rooms which have been used in the 18th century for time service and adjusting artificial satellite observations. An old 6 inch Zenith telescope has been used since 1870 for correcting the time recording by Meridian passage of stars. Two historical buildings of 1903, and many old astronomical instruments are still kept there.

　　International Services:

• Observations of the New Crescent and calculation of the beginnings of Higri (Hejira) months, for prayers and fasting in the month of Ramadan, for Egypt and for all Arab and Muslim countries. This service is unique among other observatories in the world in that it renders a vital service to Muslims in Egypt and allover the world, as they depend on the lunar calendar that was followed by Arabs throughout their history.
• Calculation of the prayer times is not the only daily service rendered to Muslims, but also definition ofthe direction ofMecca from any place in the world.
• The Helwan observatory used to host the standard meter, which was an exact replica of the one kept in Paris. After establishing the Egyptian Institute of Metrology, the meter was transferred there.