https://www.bbc.com/news/science-environment-62122859

Deepest ever!

On Monday, July 11, 2022 at 7:29:33 PM UTC-7, RichA wrote:
> On Monday, 11 July 2022 at 19:04:49 UTC-4, StarDust wrote:
> > https://www.bbc.com/news/science-environment-62122859
> >
> > Deepest ever!
>
> Stupid CNN reporter thinks the curves are "motion." Do they even READ
> the NASA info???
>
> https://www.cnn.com/2022/07/11/world/james-webb-space-telescope-first-image-scn/index.html

That's why I read the BBC.
No adds either!

>>The cluster itself isn't actually that far away - "only" about 4.6 billion light-years in the distance. But the great mass of this cluster has bent and magnified the light of objects that are much, much further away.
It's a gravitational effect; the astronomical equivalent of a zoom lens for a telescope.<<

On Monday, July 11, 2022 at 8:29:33 PM UTC-6, RichA wrote:

> Stupid CNN reporter thinks the curves are "motion." Do they even READ
> the NASA info???

I see the article has been corrected. The galaxies affected by the lensing,
in at least one part of the image, do seem to be elongated around a common
center, so it does kind of resemble how stars can be streaked by the Earth's
rotation.
But the JWST is not _on_ Earth.
What puzzles me is the diffraction spikes.
That they make six-pointed stars makes sense, what with all the hexagonal
mirrors. But there are also two smaller spikes, at a right angle to one of the
larger pairs. No doubt there's something in the telescope's construction
responsible for this, like the arms holding the secondary, but it's something I
wasn't expecting.

John Savard

On Monday, July 11, 2022 at 8:36:15 PM UTC-7, Quadibloc wrote:
> On Monday, July 11, 2022 at 8:29:33 PM UTC-6, RichA wrote:
>
> > Stupid CNN reporter thinks the curves are "motion." Do they even READ
> > the NASA info???
> I see the article has been corrected. The galaxies affected by the lensing,
> in at least one part of the image, do seem to be elongated around a common
> center, so it does kind of resemble how stars can be streaked by the Earth's
> rotation.
> But the JWST is not _on_ Earth.
> What puzzles me is the diffraction spikes.
> That they make six-pointed stars makes sense, what with all the hexagonal
> mirrors. But there are also two smaller spikes, at a right angle to one of the
> larger pairs. No doubt there's something in the telescope's construction
> responsible for this, like the arms holding the secondary, but it's something I
> wasn't expecting.
>
> John Savard

Here we go smarty, go up there an fix it!
🤗

On Monday, July 11, 2022 at 11:36:15 PM UTC-4, Quadibloc wrote:

> What puzzles me is the diffraction spikes.
> That they make six-pointed stars makes sense, what with all the hexagonal
> mirrors. But there are also two smaller spikes, at a right angle to one of the
> larger pairs. No doubt there's something in the telescope's construction
> responsible for this, like the arms holding the secondary, but it's something I
> wasn't expecting.

One of the arms of the "spider" does not line up with any of the edges of the mirror segments, so you get those spikes seen horizontally in the picture.

On Tuesday, July 12, 2022 at 7:18:14 AM UTC-6, W wrote:
> On Monday, July 11, 2022 at 11:36:15 PM UTC-4, Quadibloc wrote:
>
> > What puzzles me is the diffraction spikes.
> > That they make six-pointed stars makes sense, what with all the hexagonal
> > mirrors. But there are also two smaller spikes, at a right angle to one of the
> > larger pairs. No doubt there's something in the telescope's construction
> > responsible for this, like the arms holding the secondary, but it's something I
> > wasn't expecting.

> One of the arms of the "spider" does not line up with any of the edges of the mirror
> segments, so you get those spikes seen horizontally in the picture.

Yes, since that post, I've taken a look at an image of the JWST to refresh my memory about its
situation.

Holding the secondary in a precise position relative to the mirror with lightweight arms that
unfold in space was very difficult.

If one thinks of the overall shape of the mirror as that of a hexagon with points at the top
and bottom, the segments are hexagons with points at the left and right.

One arm, the one that extended, is at the top of the mirror, in the middle of the flat side
of a segment.

The two other arms, that only swing out, are on the points of segments. If the "top" of the
mirror is 0 degrees, the two other arms are at 150 degrees and 210 degrees.

With a shape like that, had I been thinking about what the diffraction pattern of the
telescope would look like, I would have been expecting _twelve_ diffraction spikes
in two groups of six rather than just six plus two. Perhaps a closer look will turn up
more tiny little diffraction spikes.

John Savard

On Tuesday, July 12, 2022 at 11:54:58 AM UTC-6, Quadibloc wrote:

> With a shape like that, had I been thinking about what the diffraction pattern of the
> telescope would look like, I would have been expecting _twelve_ diffraction spikes
> in two groups of six rather than just six plus two. Perhaps a closer look will turn up
> more tiny little diffraction spikes.

I've just looked at the full-resolution version of that image, with additional zoom,
on my computer. Yes, there are more diffraction spikes. Less bright stars show
a six-plus-six spike pattern; the bright ones, where two horizontal spikes are prominent,
also show not only those four additional spikes, but some at in-between positions that
do not appear to be at angles that are exactly halfway. And then still other spikes,
making a total of 48 spikes for the brightest stars in the image!

John Savard

On Tuesday, July 12, 2022 at 11:07:06 AM UTC-7, Quadibloc wrote:
> On Tuesday, July 12, 2022 at 11:54:58 AM UTC-6, Quadibloc wrote:
>
> > With a shape like that, had I been thinking about what the diffraction pattern of the
> > telescope would look like, I would have been expecting _twelve_ diffraction spikes
> > in two groups of six rather than just six plus two. Perhaps a closer look will turn up
> > more tiny little diffraction spikes.
> I've just looked at the full-resolution version of that image, with additional zoom,
> on my computer. Yes, there are more diffraction spikes. Less bright stars show
> a six-plus-six spike pattern; the bright ones, where two horizontal spikes are prominent,
> also show not only those four additional spikes, but some at in-between positions that
> do not appear to be at angles that are exactly halfway. And then still other spikes,
> making a total of 48 spikes for the brightest stars in the image!
>
> John Savard

I like it!
The more spikes the better!

On Tuesday, July 12, 2022 at 9:18:14 AM UTC-4, W wrote:
> On Monday, July 11, 2022 at 11:36:15 PM UTC-4, Quadibloc wrote:
>
> > What puzzles me is the diffraction spikes.
> > That they make six-pointed stars makes sense, what with all the hexagonal
> > mirrors. But there are also two smaller spikes, at a right angle to one of the
> > larger pairs. No doubt there's something in the telescope's construction
> > responsible for this, like the arms holding the secondary, but it's something I
> > wasn't expecting.

> One of the arms of the "spider" does not line up with any of the edges of the mirror segments, so you get those spikes seen horizontally in the picture.

https://www.reddit.com/r/jameswebb/comments/th5jl6/explaining_the_difraction_spikes_in_jwst_images/

The Spider is added in with the right-most image and the horizontal spike appears to extend.

On Tue, 12 Jul 2022 11:07:04 -0700 (PDT), Quadibloc
<jsavard@ecn.ab.ca> wrote:

>On Tuesday, July 12, 2022 at 11:54:58 AM UTC-6, Quadibloc wrote:
>
>> With a shape like that, had I been thinking about what the diffraction pattern of the
>> telescope would look like, I would have been expecting _twelve_ diffraction spikes
>> in two groups of six rather than just six plus two. Perhaps a closer look will turn up
>> more tiny little diffraction spikes.
>
>I've just looked at the full-resolution version of that image, with additional zoom,
>on my computer. Yes, there are more diffraction spikes. Less bright stars show
>a six-plus-six spike pattern; the bright ones, where two horizontal spikes are prominent,
>also show not only those four additional spikes, but some at in-between positions that
>do not appear to be at angles that are exactly halfway. And then still other spikes,
>making a total of 48 spikes for the brightest stars in the image!

You might be interested in the technical analysis of the JWST PSF:
https://www.stsci.edu/files/live/sites/www/files/home/jwst/documentation/technical-documents/_documents/JWST-STScI-001157.pdf

The pattern changes considerably with the filter that is used, as it
is wavelength dependent.

On Tuesday, July 12, 2022 at 11:12:45 PM UTC-6, Chris L Peterson wrote:

> The pattern changes considerably with the filter that is used, as it
> is wavelength dependent.

I did pick that document up from a link in the article W linked to.

And I noticed that the diffraction spikes varied in color in the images,
but I didn't read the paper closely enough to find out why the diffraction
pattern would be wavelength-dependent.

John Savard

On Wednesday, July 13, 2022 at 9:53:55 PM UTC-4, Quadibloc wrote:
> On Tuesday, July 12, 2022 at 11:12:45 PM UTC-6, Chris L Peterson wrote:
>
> > The pattern changes considerably with the filter that is used, as it
> > is wavelength dependent.
> I did pick that document up from a link in the article W linked to.
>
> And I noticed that the diffraction spikes varied in color in the images,
> but I didn't read the paper closely enough to find out why the diffraction
> pattern would be wavelength-dependent.

https://www.google.com/search?client=firefox-b-1-d&q=diffraction+formula

The two sources of diffraction are at different distances from the focal surface.

This is also a false-color image, so maybe things are not quite as one would expect?