Starship Asterisk*

Guest wrote:
Speaking of diffraction spikes, could we do without lenses and mirrors if we could make a flat CCD like detector that captures all the necessary electromagnetic information such as intensity, direction, wavelength, etc?

With a strong artificial coherent source one can fairly easily record standing waves as holograms.

Weak natural incoherent sources are somewhat more problematic.

Guest wrote:
Doesn't all the information that reaches the Hubble telescope pass through an imaginary flat circle?

Yes... but lens, mirrors and diffraction gratings do a wonderful job of transforming traveling waves of a specific intensity, direction, wavelength onto a well defined flat CCD detector (Airy) spot. This is why holograms are not more ubiquitous and why the initial interferometer idea was finally dropped for the Gaia (spacecraft).

BMAONE23 wrote:
Diffraction spikes could be eliminated by suspending the secondary mirror in the center of a sheet of synthetic sapphire. Like what is used for scratch resistant watch lenses. You could even shape the sapphire as a one piece clear mirror support/mirror and coat the center section to create the secondary sapphire mirror

Or a flat piece of glass.

(A neutral-gray tinted piece of glass
could also be used as an APODization filter.)

It is curious that the galaxies in the Deep Field survey do not appear to look as predicted according to the Big Bang model. There are many elliptical galaxies, which are typically much older than spirals (http://en.wikipedia.org/wiki/Elliptical_galaxy). The distribution, size, and composition of the galaxies in the survey appears to contradict the idea that they all very young (within ~.3 Gyr of the Big Bang). We also note in the background of the image contains numerous faint other galaxies; there appears to be no limit to the depth of the field in the photograph. Could the redshift data have been somehow misinterpreted? Can red-shift of light occur in ways not necessarily relating to the movement of the source object? One is reminded of the "Tired Light" theory put forth by Fritz Zwicky in 1929 in response to Hubble's data (http://en.wikipedia.org/wiki/Tired_light).

DrEdwinEinst wrote:We also note in the background of the image contains numerous faint other galaxies

"We"? Who, pray tell, is we?

...astronomers have now solved a decade-long mystery as to how compact elliptical-shaped galaxies existed when the universe was so young. These "red and dead" galaxies have now been linked directly to an earlier population of dusty starburst galaxies. These objects voraciously used up available gas for star formation very quickly. Then they grew slowly through merging as the star formation in them was quenched, and they eventually became giant elliptical galaxies.

Source: http://hubblesite.org/newscenter/archiv ... s/2014/10/

And the full press release is here: http://hubblesite.org/newscenter/archiv ... 4/10/full/

Neufer wrote "Apodization". My first though was WHY? So I bravely clicked the link and landed in the middle of a Neufonian type explanation of "something". So I scrolled a very little to the top of the Wikipedia page, where things miraculously made sense. First, it said that this article may be confusing or unclear to readers. That's an understatement of truth, if I've ever heard one. But a sentence or so later, the article said Apodization literally means "Removing the foot". Why, heck, it all became simple to understand. My shoes and or slippers and socks under go "Apodization" each day, late at night. Why, it could even be used with owlice's signature, to make it more 'techy'. "A closed mouth needs no Apodization of foot".
So thanks for the really neat simple and confusing post, neufer. As usual, it's a work of Art.

BMAONE23 wrote:Diffraction spikes could be eliminated by suspending the secondary mirror in the center of a sheet of synthetic sapphire. Like what is used for scratch resistant watch lenses. You could even shape the sapphire as a one piece clear mirror support/mirror and coat the center section to create the secondary sapphire mirror

Or you could use a refractor, which has no central obstruction. Either way, however, you'll have diffraction artifacts. Instead of spikes and rings, you'll just have rings.

Guest wrote:Speaking of diffraction spikes, could we do without lenses and mirrors if we could make a flat CCD like detector that captures all the necessary electromagnetic information such as intensity, direction, wavelength, etc? Doesn't all the information that reaches the Hubble telescope pass through an imaginary flat circle?

Such a detector would still show diffraction spikes, assuming it was square. Optically, the detector itself would act as an aperture. If the detector was round, you'd get diffraction rings.

You just can't fool mother nature.

Chris Peterson wrote:

Guest wrote:Speaking of diffraction spikes, could we do without lenses and mirrors if we could make a flat CCD like detector that captures all the necessary electromagnetic information such as intensity, direction, wavelength, etc? Doesn't all the information that reaches the Hubble telescope pass through an imaginary flat circle?

Such a detector would still show diffraction spikes, assuming it was square. Optically, the detector itself would act as an aperture. If the detector was round, you'd get diffraction rings.

You just can't fool mother nature.

People aren't going to know what to do when they see Webb's diffraction patterns. There are some simulated ones available already. Combined into RGB images, they look like this: