Hubble Deep Space Image Question?

Question

I heard they had the shutter opened for 11 days... How did they get such a clear image? I mean the telescope is orbiting the earth so even the slightest movement will cause bluriness...

Answer 1

The magic of computer technology is the quick answer. It can be very accurately aimed and it's orbit isn't always geosynchronus.

If for example, it was looking perpendicular to its orbital plane, then the corrections for this would only have to take into account the slightest wobble, as you would when looking at a cars wheel turning 100's of metres away..

With enough distance from Earth and the galaxy, the universe is uniform in it's distribution, so it isn't restricted to viewing along any orbital plane, solar or galactic..

Answer 2

The following is from the Hubble News Archive from 1996...

Nearly a year of preparation preceded the observation. The HDF team selected a piece of sky near the handle of the Big Dipper (part of the northern circumpolar constellation Ursa Major, the Great Bear). The field is far from the plane of our Galaxy and so is "uncluttered" of nearby objects, such as foreground stars. The field provides a "peephole" out of the galaxy that allows for a clear view all the way to the horizon of the universe.

Test exposures made in early 1995 with Hubble and the 4-meter telescope at Kitt Peak National Observatory also confirmed the field is devoid of large galaxy clusters, which would interfere with seeing farther and fainter objects. The target field is, by necessity, in the continuous viewing zone (CVZ) of Hubble's orbit, a special region where Hubble can view the sky without being blocked by Earth or interference from the Sun or Moon.

Staring at one spot in the sky for ten days, Hubble kept taking pictures one after another for the entire exposure time, accumulating data. Each exposure was typically 15 to 40 minutes long. Separate images were taken in ultraviolet, blue, red, and infrared light. By combining these separate images into a single color picture, astronomers will be able to infer — at least statistically — the distances, ages, and composition of the galaxies in the HDF image.

Astronomers at ST ScI processed the frames, removing cosmic rays and other artifacts, and put them together into one final picture. Each time they add a picture, the view got deeper, revealing fainter objects. When they were done they had the deepest picture ever taken of the heavens.

Answer 3

Firstly, Hubble has excellent stationkeeping systems, allowing it to point at one spot continuously and maintain a high degree of stability while doing so. Secondly, the orbit is only a few thousand miles in diameter, and what the telescope was looking at was millions, even billions, of light years away. The movement in its orbit won't cause much of a problem there. It's like taking a picture of a mountain range from ten miles away and stepping a foot to the left. Any foreground objects would shift, but the background won't.

Answer 4

This is a testament to the stability of this telescope and the sensitivity of the gyros that stabilize it.

Answer 5

http://hubblesite.org/the_telescope/