Re: Question about telescope design.

On 27 Jan, 02:10, br...@xxxxxxx (Brian Tung) wrote:
markzoomwrote:
There could be adjustments, so it wouldn't need to have the same level
of precision.

You're brushing a large level of difficulty facilely under the rug.

On the contrary. It is apparently a new concept for which the easiest
methods have simply not yet been explored.

For a bit of incentive check out some links on scanning digital
cameras and the huge resolutions they can achieve.



might as well say that with a large lighthouse mirror, whose area kicks
that of a 3 m strip up and down the block.

Or you could start thinking of ways to actually do it.

Someone mentioned that the strip should be curved both ways, like a
slice from the mirror of a normal telescope.
OK, I'd say one could achieve that too. If a *** of glass is rested
in a jig with the middle raised (IE the edges droop a set amount), and
the top ground flat, it would spring back with the convex ground in.

The whole thing doesn't even have to be a symmetrical parabolic, it
could be a strip from any part of the parabola as long as the sensor
is mounted in the appropriate place.



BTW, why are people asking me how to do it instead of proposing
solutions?

Those questions are rhetorical. They are meant to indicate that the
problems are not practically solvable by any amateur (whom, presumably,
you are suggesting this for).

It sounds more like people are not engaging their minds for
solutions...


Is there no one here with any design engineering abilities?

There is no one here with the requisite engineering abilities to build
support structures to that level of precision, and the promised payoff
doesn't seem good enough, since the strip doesn't have the benefit of
large area, and it is really large area, not width, that confers the
resolution and brightness benefits of large-aperture mirrors. (You do
get some resolution benefit from large width, but it's only in one
dimension. And this resolution benefit is at the mercy of the seeing,
too.)

You're wrong, we've made one axis superfluous because we are scanning.
according to this (not very good) example it says a $10k scanning
camera can achieve resolutions of 500k-1GB in one photo:
http://tinyurl.com/2vth9r

That might be achievable. Off the top of my head:
If you imagine a *** of glass cut to the shape of a sickle (the
inner cut edge being the reflective part) I would think that
compressing (squashing) the *** at strategic points near the edge
could make adjustments in that range at the reflective edge.

Again, you cannot cut anything to that level of precision. Mirrors for
telescopes are not cut, they are ground. The blanks start out with
surfaces whose radius of curvature varies all over the place. However,
as the grinding process wears on (pun intended), points of greater
curvature on one surface rub up against points of lesser curvature on
the other, evening things out. After some time (and lots of elbow
grease), you have accurate spheres.

Yes, I know the vagueries of lens grinding. Obviously we to grind the
*edge* of a *** of glass and obviously we need to devise an method
to do this. Just because there hasn't been a need to do it doesn't
mean there isn't a simple way.


You started out this thread asking if this would work. It seems to me
that you really don't want the negative answer. That's OK, but it also
seems counterproductive to ask a question you only really want one
answer to.

What I want is people to engage their brains. Most inventions have
been thought impossible before the obstacles were overcome, often in
amazingly simple ways.
I doubt that bending and fixing a reflective strip into the right
curvature is beyond rocket science.


--
Brian Tung <br...@xxxxxxx>
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