how much is the resolution of hubble's image?

Answer 1

The Hubble's primary mirror is 2.4 m wide. Not as big as many ground-based telescopes, but being in space it doesn't have to contend with atmospheric "seeing."

The formula for calculating resolving power from aperture is:
R = 1.22*w/D
where R is the resolution in radians,
w is the wavelength of light,
D is the diameter if the lens,
and 1.22 is a constant calculated by some smart guy named Raleigh.

For the Hubble, it looks like this:
R = 1.22*580nm / 2.5 m = 3*10^-7 radians. (580 nm is the wavelength of yellow light, about the midrange of the visual spectrum.)

To convert radians to arc-seconds, 3*10^-7 * (648,000/pi) = 0.06 arc-seconds.

So ideally, 0.06 arc-seconds. However, it's a historical fact the subcontractor who made the mirror for NASA botched it so its resolution is less than ideal. But with corrective optics installed, it's resolution is roughly 0.1 arc-seconds. This is still about 10 times better that the 1.0 arc-second most ground based telescopes can achieve (due to the limitations of viewing in atmosphere.)

To put this in perspective, looking at the Earth from a distance of 600 km, it can resolve objects as small as 30 cm. Looking at the Moon from 375,000 km, it can resolve objects as small as 360 m. (Sorry, moon buggies and flags too small to see.) And looking at Mars, 75 million km distant at conjunction, objects as small as 36 km wide can be made out.

Answer 2

The Hubble Space Telescope has a stated resolution of 0.1 arc-seconds per pixel, based on the original design specifications. However, the spherical aberration of the main mirror, caused by the faulty grinding, required the design fitting of a corrective lens to restore the original resolution.

At the distance to the moon, 0.1 arc-second converts to a "spot" (pixel) that covers an area about 15-20 meters in diameter.

Answer 3

Hubble is a 2.4 meter telescope. That is 94.5 inches. Resolving power in visible light can be easily expressed with Dawes's limit at 4.56/94.5 = 0.048 arc seconds. That is 0.000013 degrees. So how small an object is that at different distances? It is a 295 foot object on the Moon or an 8 mile wide object on Mars at closest approach, or a 930 mile wide object on Pluto or a 5.8 million mile wide object at the nearest star or a 930 light year wide object in a galaxy 4 billion light years away. Since galaxies are MUCH bigger than 930 light years, Hubble can easily see galaxies that far away and still not see a flag on the Moon.

Or a 7 inch object 500 miles away, on Earth directly below. Spy satellites are telescopes as big as Hubble but pointed at Earth. But you aren't supposed to know that, so now I have to kill you.

Answer 4

..."the two main advantages that a space-based observatory would have over ground-based telescopes. First, the angular resolution (smallest separation at which objects can be clearly distinguished) would be limited only by diffraction, rather than by the turbulence in the atmosphere, which causes stars to twinkle and is known to astronomers as seeing. [At that time ground-based telescopes were limited to resolutions of 0.5–1.0 arcseconds, compared to a theoretical diffraction-limited resolution of about 0.1 arcsec for a telescope with a mirror 2.5 m in diameter.] Second, a space-based telescope could observe infrared and ultraviolet light, which are strongly absorbed by the atmosphere"
The HST mirror is 2.4 m in diameter, so the resolution may be near the goal of about 0.1 arcsec. As the HST can see the UV, a better resolution would be available (due to the shorter wavelengh)

Answer 5

It can get up to millions of pixels. Hundreds of millions. The Hubble can take an image with one camera, or stictch together multiple images.