Starship Asterisk*

madman56 wrote:Is the atmosphere above northern Africa really that transparent? Why aren't there more observatories there?

APOD Robot wrote:If you were to sit on the surface of the Moon, you would see the Earth just hang in the sky.

Chris Peterson wrote:

madman56 wrote:
Is the atmosphere above northern Africa really that transparent? Why aren't there more observatories there?

The atmosphere everywhere is very transparent, assuming no clouds. Transparency isn't usually the primary factor we look for when siting observatories. What is generally more important is the total column of air we're looking through, since that affects the steadiness of the image. This is also impacted by regional airflow patterns. And, of course, weather is important. The Sahara is often cloud free, which is good. But in other respects, it is not.

• Keeping dust out will always be a problem for both lunar & North African observatories.

http://www.nriag.sci.eg/?page_id=574 wrote:

[b][color=#0000FF][size=150]The dome of Kottamia telescope[/size][/color][/b]

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<<Kottamia astronomical observatory is the largest telescope in the Arab world, the Middle East and North Africa. The diameter of the 2 ton main mirror is about 74 inches. This telescope is located approximately at 80 km from the center of the capital “Cairo” in the direction of the Suez city over a mount rises 450 meters above sea level. The Observatory established in 1964, as an extension of Helwan observatory, which was established in 1903, one of the oldest research institutes in Egypt and the Middle East.

The observatory building made of double walls; completely isolated from the desert environment surrounding it. The Telescope’s Dome made of double walls of steel. The diameter of the dome is about 19 meters, and weighs more than 100 tons. It revolves around the building upon 26 rods of steel, and the bottom edges of the Telescope’s dome prevent leakage of dust and heat to the interior, and this design makes the temperature of the floor not exceed than 3oC even in the hot days.>>

• Sadly, the Golden Age of Islamic astronomy was over five centuries ago:

https://en.wikipedia.org/wiki/Astronomy_in_the_medieval_Islamic_world wrote:
<<Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (8th–15th centuries), and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. 1450–1900: The period of stagnation, when the traditional system of astronomy continued to be practised with enthusiasm, but with rapidly decreasing innovation of any major significance.>>

Chris Peterson wrote:

APOD Robot wrote:
If you were to sit on the surface of the Moon, you would see the Earth just hang in the sky.

There is nearly half of the lunar surface where you could stand and never see the Earth at all.

• But "APOD Robot" was only talking about "sitting" on the lunar surface.

https://en.wikipedia.org/wiki/Libration#Lunar_libration wrote:
<<Over time, about 59% of the Moon's surface is seen from Earth due to libration.>>

Jim Armstrong wrote:
I wonder why that particular part of the Earth's surface seems to be by far the most commonly portrayed.

• Everything must be compared to the iconic December 7 Blue Marble photograph over Africa:

https://en.wikipedia.org/wiki/The_Blue_Marble wrote:

[b][color=#0000FF][size=150]The Blue Marble[/size][/color][/b]

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<<The Blue Marble is a famous photograph of the Earth, taken on December 7, 1972, by the crew of the Apollo 17 spacecraft, at a distance of about 45,000 kilometers. It is one of the most iconic, and among the most widely distributed images in human history. Apollo 17 was the first night launch of a U.S. human spaceflight and the last manned lunar mission. No one since has been far enough from Earth to photograph a whole-Earth image such as The Blue Marble.

The photograph was taken about 5 hours and 6 minutes after launch of the Apollo 17 mission, and about 1 hour 54 minutes after the spacecraft left its parking orbit around the Earth, to begin its trajectory to the Moon. The time of Apollo 17's launch, 12:33 a.m. EST, meant that Africa was in daylight during the early hours of the spacecraft's flight. With the December solstice approaching, Antarctica was also illuminated.

Counterculture activists had been among the first to cherish these images as icons of a new global consciousness. The Apollo 17 image, however, released during a surge in environmental activism during the 1970s, became a symbol of the environmental movement, as a depiction of Earth's frailty, vulnerability, and isolation amid the vast expanse of space.>>

geckzilla wrote:
The most commonly portrayed part of Earth's surface for me is the American facing side. Real, actual space photos aside, almost every illustration I see shows North and South America. This is probably because I am American and I mostly view American media.

https://en.wikipedia.org/wiki/Geostationary_Operational_Environmental_Satellite wrote:

[b][color=#0000FF]The first image obtained from the GOES 1 satellite, 1975 October 25[/color][/b]

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<<The Geostationary Operational Environmental Satellite system (GOES), operated by the United States' National Environmental Satellite, Data, and Information Service (NESDIS), supports weather forecasting, severe storm tracking, and meteorology research. Spacecraft and ground-based elements of the system work together to provide a continuous stream of environmental data. The National Weather Service (NWS) uses the GOES system for its United States weather monitoring and forecasting operations, and scientific researchers use the data to better understand land, atmosphere, ocean, and climate interactions.

The GOES system uses geosynchronous satellites which—since the launch of SMS-1 in 1974—have been a basic element of U.S. weather monitoring and forecasting.

GOES 13 is designated GOES-East, currently located at 75°W. It was placed in orbit on 24 May 2006, underwent Post-Launch Testing through early 2007, then replaced GOES 12 as GOES-East.>>

Beyond wrote:
I say we GOES West a bit and get the US of A in the picture. I'm a bit weary of seeing African desert.

neufer wrote:

Beyond wrote:
I say we GOES West a bit and get the US of A in the picture. I'm a bit weary of seeing African desert.

http://goes.gsfc.nasa.gov/goescolor/goe ... stfull.jpg
http://goes.gsfc.nasa.gov/goescolor/goe ... stfull.jpg

neufer wrote:

Beyond wrote:
I say we GOES West a bit and get the US of A in the picture. I'm a bit weary of seeing African desert.

http://goes.gsfc.nasa.gov/goescolor/goe ... stfull.jpg
http://goes.gsfc.nasa.gov/goescolor/goe ... stfull.jpg

Jeddo wrote:Given the moon's libration https://en.wikipedia.org/wiki/Libration#Lunar_libration the Earth is not hanging in the same spot of the Moon's sky but tracking an irregular circle – and judging by the significant wobble I would expect this circle to be larger than the Earth's diameter. Consequently, standing on a convenient spot on the Moon's horizon, you _would_ see earthrises and earthsets, though of course not in the opposite directions of the horizon but occurring rather close to each other. One each in 28-odd Earth days.