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Originally posted by Mizar
I'm not saying your wrong Murcielago, Actually I don't doubt that your right. I'm just wondering how they did the Hubble Deep Feilds like that? I was always under the impression that the HDFs were doen over days exposure.
[edit on 16-8-2005 by Mizar]
That was a pretty good explanation, except that its wrong
Hubble was pointed at the same patch of sky for several cumulative days and took long exposures. Scientist were surprised to find a bewildering assortment of at least 10,000 galaxies at various stages of evolution.
I dont like to repeat myself.
Just read more closely what he wrote and what I wrote.
The Hubble is in LEO orbit, its phisically impossable to view on spot for much longer then 45 minutes, because it orbits so close to the earth
But all objects, including telescopes, also emit infrared light. To avoid swamping the very faint astronomical signals with radiation from the telescope, the telescope and its instruments must be very cold. Therefore, JWST has a large shield that blocks the light from the Sun, Earth, and Moon, which otherwise would heat up the telescope, and interfere with the observations. To have this work, JWST must be in an orbit where all three of these objects are in about the same direction.
In order to do this, JWST will have a much larger primary mirror than Hubble (2.5 times larger in diameter, or about 6 times larger in area), giving it much more light gathering power. It also will have better infrared instruments than Hubble, allowing it to see the formation of stars and galaxies (see below). Finally, JWST will operate much farther from Earth, where operations are simpler, and where giving the telescope a stable pointing is easier than with the Earth-orbiting Hubble
JWST is designed to discover and study the first stars and galaxies that formed in the early Universe. To see these faint objects, it must be able to detect things that are ten billion times as faint as the faintest stars visible without a telescope. This is 10 to 100 times fainter than Hubble can see.
The fact that Hubble is in orbit around the earth and cannot spot onto any area for more than 45 minutes has nothing to do with the fact that it cannot distinguish another planet from its sun.
Nope, it can't observe earth's surface because our planet rotates too fast.
Originally posted by mashup
as it's able to see a books pages perfectly from where it's orbiting us.