Re: Fixing an unfocused image theoretically straightforward?!

On Apr 20, 3:46 pm, d...@xxxxxxxxx (Dave Martindale) wrote:
JimAtQuarktet <c...@xxxxxxxxxxxx> writes:
If there was a good way to fix this using software, the Hubble
Telescope wouldn't have needed a $700M repair mission.
If the Hubble sensor was essentially noiseless, and had a very large
bit depth, a deconvolution may have been able to prevent the $700M
repair mission.

Also if the cameras had infinite intensity resolution, which no real
camera does.

Hubble's mirror is not very large by ground telescope standards, even at
the time it was launched, but it was supposed to be able to see very dim
objects because the lack of atmosphere and (supposedly) very accurate
and smooth optics would concentrate most the light from the star into a
0.1 arcsecond span of pixels at the prime focus. But in fact the
focused star image had a point spread function something like 1 arc
second in size, so the same amount of light was spread over 100 times as
many pixels. The light from faint stars could no longer be reliably
detected above the noise.

So Hubble got used to image brighter things for a while, things that
could be captured and sharpened by image processing. But it wasn't
until the optics were fixed that it could be used for faint-object
work.

Dave

In fact the optics were superbly smooth, about 1/40th wave in green
light. But, the perfect Kodak mirror was on the ground while the
improperly ground (the shape, not the surface quality) was in the
telescope and horribly spherically aberrated. And, Hughes Danbury
Optical Systems (who made the error) never really paid back what it
cost to fix it
using compensating optics called, "Costar."

.

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