best of Hubble images

Nicholas O. Lindan wrote:
"Paul Furman"

"Focal reducers are positive lenses which do two things ..."
The only similar thing I've heard of is

A close-up lens.

It reduces the lens focal length, but the lens stays in the
same spot

Does it reduce the focal length? If I focus a 'bare' lens at closest
distance, then put a closeup lens on the end I have to crank it to
infinity to get back in focus (and move in closer). For a simple lens
design, cranking to infinity actually *increases* the focal length.

so the new reduced focal length lens is now focused
pretty close.

It increases the aperture - the new lens is faster - but as
it is extended for close up the bellows correction (close-up
correction) compensates and the effective f-stop is the original
lens f-stop.

If you put a close-up lens on a view camera, where you can
rack the lens closer to the film, you get a usable shorter
lens.

There are negative "anti-close-up lenses(?)" used with
view cameras to increase focal length. Not used much anymore.

Paul Furman wrote:
Nicholas O. Lindan wrote:
"Paul Furman"

"Focal reducers are positive lenses which do two things ..."
The only similar thing I've heard of is

A close-up lens.

It reduces the lens focal length, but the lens stays in the
same spot

Does it reduce the focal length? If I focus a 'bare' lens at closest
distance, then put a closeup lens on the end I have to crank it to
infinity to get back in focus (and move in closer). For a simple lens
design, cranking to infinity actually *increases* the focal length.

Oh, sorry, I had that backwards. You are right.

so the new reduced focal length lens is now focused
pretty close.

It increases the aperture - the new lens is faster - but as
it is extended for close up the bellows correction (close-up
correction) compensates and the effective f-stop is the original
lens f-stop.

If you put a close-up lens on a view camera, where you can
rack the lens closer to the film, you get a usable shorter
lens.

There are negative "anti-close-up lenses(?)" used with
view cameras to increase focal length. Not used much anymore.

[A complimentary Cc of this posting was sent to
Robert Sneddon
], who wrote in article :
Those defects bite into its light grasp and resolution. A new Hubble
would have a perfect mirror day one resulting in better science day two.
The problems with the solar cells are known and would be fixed in the
new design etc. etc.

LOL! Have not you forgot they said it about the Hubble I too? :-(

Yours,
Ilya

In message , Ilya Zakharevich
writes
[A complimentary Cc of this posting was sent to
Robert Sneddon
], who wrote in article bc0BFEVc4MyHFw1H@nosp
am.demon.co.uk:
A new Hubble
would have a perfect mirror day one resulting in better science day two.
The problems with the solar cells are known and would be fixed in the
new design etc. etc.

LOL! Have not you forgot they said it about the Hubble I too? :-(

They didn't say that about the Hubble which was a very experimental
satellite in more ways than one. The mirror wasn't tested properly, in
part to save money. This was a Bad Idea. The problems with the solar
cell panels (the largest ever deployed on a scientific satellite up to
that time) were actually foreseen, in fact. Sadly for the Hubble
designers, the people who knew there were going to be problems with the
panels were the people who had designed similar panels for the American
Keyhole spy satellites and they had to keep their mouths shut for
security reasons.
--
To reply, my gmail address is nojay1 Robert Sneddon

[A complimentary Cc of this posting was sent to
Robert Sneddon
], who wrote in article :
A new Hubble
would have a perfect mirror day one resulting in better science day two.
The problems with the solar cells are known and would be fixed in the
new design etc. etc.

LOL! Have not you forgot they said it about the Hubble I too? :-(

They didn't say that about the Hubble which was a very experimental
satellite in more ways than one.

Yes, they did. [It was less than 40 years ago. Is your memory that
short? ;-]

The mirror wasn't tested properly, in
part to save money. This was a Bad Idea. The problems with the solar
cell panels (the largest ever deployed on a scientific satellite up to
that time) were actually foreseen, in fact. Sadly for the Hubble
designers, the people who knew there were going to be problems with the
panels were the people who had designed similar panels for the American
Keyhole spy satellites and they had to keep their mouths shut for
security reasons.

I do not follow: are you implying this won't happen to Hubble II ?!

Yours,
Ilya

In message , Ilya Zakharevich
writes

], who wrote in article ff1wV0HZQbyHFwFH@nosp
am.demon.co.uk:
The mirror wasn't tested properly, in
part to save money. This was a Bad Idea. The problems with the solar
cell panels (the largest ever deployed on a scientific satellite up to
that time) were actually foreseen, in fact. Sadly for the Hubble
designers, the people who knew there were going to be problems with the
panels were the people who had designed similar panels for the American
Keyhole spy satellites and they had to keep their mouths shut for
security reasons.

I do not follow: are you implying this won't happen to Hubble II ?!

The mirror of a Hubble II *will* be tested properly and the solar cell
panel design will not have the vibration and deployment problems the
Hubble I did. Those are some of the lessons learned from the first
version. Of course it's entirely possible a Hubble II will have other
problems as it's likely to be experimental in other ways.
--
To reply, my gmail address is nojay1 Robert Sneddon

[A complimentary Cc of this posting was sent to
Robert Sneddon
], who wrote in article :
The mirror wasn't tested properly, in
part to save money. This was a Bad Idea. The problems with the solar
cell panels (the largest ever deployed on a scientific satellite up to
that time) were actually foreseen, in fact. Sadly for the Hubble
designers, the people who knew there were going to be problems with the
panels were the people who had designed similar panels for the American
Keyhole spy satellites and they had to keep their mouths shut for
security reasons.

I do not follow: are you implying this won't happen to Hubble II ?!

The mirror of a Hubble II *will* be tested properly and the solar cell
panel design will not have the vibration and deployment problems the
Hubble I did. Those are some of the lessons learned from the first
version. Of course it's entirely possible a Hubble II will have other
problems as it's likely to be experimental in other ways.

Of course; this WAS my point. There are 3 factors to consider:

a) lessons learned and accumulated in the published literature;
b) availability of people to chat with who learned the "previous lessons";
c) degree of "experimentality" of the platform.

So if one could launch the exact replica of Hubble I, AND one could
collect all the people on Hubble I team together, it would have been
a perfect mission.

But it is NOT POSSIBLE to collect all these people together; and, IMO,
"b" is much more important than "a"! AFAIK, the space programs are
practically dead now (except for Chinese? - do not know anything about
them). My estimates are that "b" has almost disappeared.

So even the exact replica would have a lot of possibilities to go
havoc. [And, speaking of "a", I've heard a rumor that (what was
available of) blueprints of Saturn V are lost. (AFAIK, some
late-moments additions were never reflected in blueprints, just in
people's memory.)]

Hope this helps,
Ilya