BeechTalk - BT

Username Protected · **Posted:** 12 Feb 2022, 13:49

Username Protected wrote:

CCD cameras also benefit from cooling the sensor. Also shot noise (thermionic emission) is temperature dependent.

True. Since they quit using film, most observatory cameras use cyrogenically cooled detectors which allows for much longer exposure times than you could have at room temperature.

Username Protected · **Posted:** 16 Mar 2022, 18:03

It works!

Username Protected · **Posted:** 16 Mar 2022, 18:20

Mirror alignment almost completed:

https://arstechnica.com/science/2022/03 ... telescope/

Username Protected · **Posted:** 16 Mar 2022, 21:03

Alignment Milestone, Optics Working Successfully

Exciting news.

Image here.

Username Protected · **Posted:** 17 Mar 2022, 00:17

I thought that alignment was supposed to take a few months?

Username Protected · **Posted:** 17 Mar 2022, 00:21

Username Protected wrote:

I thought that alignment was supposed to take a few months?

I think this was just one key step. They put together a great website: https://www.jwst.nasa.gov/content/webbL ... er.html#30

Username Protected · **Posted:** 17 Mar 2022, 08:19

Username Protected wrote:

I thought that alignment was supposed to take a few months?

"Over the next six weeks, the team will proceed through the remaining alignment steps before final science instrument preparations. The team will further align the telescope to include the Near-Infrared Spectrograph, Mid-Infrared Instrument, and Near InfraRed Imager and Slitless Spectrograph. In this phase of the process, an algorithm will evaluate the performance of each instrument and then calculate the final corrections needed to achieve a well-aligned telescope across all science instruments. Following this, Webb’s final alignment step will begin, and the team will adjust any small, residual positioning errors in the mirror segments.

The team is on track to conclude all aspects of Optical Telescope Element alignment by early May, if not sooner, before moving on to approximately two months of science instrument preparations. Webb’s first full-resolution imagery and science data will be released in the summer."

From the NASA news material posted.

Username Protected · **Posted:** 17 Mar 2022, 10:09

Username Protected wrote:

It works!

Hope that's not Starman's headlight.

Username Protected · **Posted:** 17 Mar 2022, 10:32

Take a close look at the large image I linked to earlier (here).

To quote Dave Bowman at the end of 2001: A Space Odyssey, "My god, it's full of stars." In this case, distant galaxies of many types.

Although this is a test image, it recalls the famous Hubble deep-field image

Username Protected · **Posted:** 17 Mar 2022, 12:14

It'd be nice if they could get rid of the horrendous lens flare.

Username Protected · **Posted:** 17 Mar 2022, 12:25

From a BBC story:

Quote:

The "spike" structures were a function of the design of Webb's primary mirror, explained Mark McCaughrean from the European Space Agency (Esa).

"The shape of those 18 hexagons imprints a faint diffraction pattern that makes bright stars look like spiky snowflakes - this isn't a problem for the science, but will give Webb images a very distinctive look," he told BBC News.

"Indeed, the fact that we can see those spikes so crisply also confirms that the mirrors have been perfectly lined up - this is brilliant news."

Username Protected · **Posted:** 17 Mar 2022, 12:29

Username Protected wrote:

From a BBC story:

Quote:

The "spike" structures were a function of the design of Webb's primary mirror, explained Mark McCaughrean from the European Space Agency (Esa).

"The shape of those 18 hexagons imprints a faint diffraction pattern that makes bright stars look like spiky snowflakes - this isn't a problem for the science, but will give Webb images a very distinctive look," he told BBC News.

"Indeed, the fact that we can see those spikes so crisply also confirms that the mirrors have been perfectly lined up - this is brilliant news."

Wooh... Thank goodness. When I saw those spiky things I thought surely we were going to have to put a mask on the telescope...

Username Protected · **Posted:** 17 Mar 2022, 14:06

Username Protected wrote:

From a BBC story:

Quote:

The "spike" structures were a function of the design of Webb's primary mirror, explained Mark McCaughrean from the European Space Agency (Esa).

"The shape of those 18 hexagons imprints a faint diffraction pattern that makes bright stars look like spiky snowflakes - this isn't a problem for the science, but will give Webb images a very distinctive look," he told BBC News.

"Indeed, the fact that we can see those spikes so crisply also confirms that the mirrors have been perfectly lined up - this is brilliant news."

So it's blurry by design. :doh:

Username Protected · **Posted:** 17 Mar 2022, 14:16

so I zoomed in on that initial picture. it is captivating.

if you looks closely, you can see a few "rings of light." i.e., a black dot with a ring of starlight around it. could these be black holes, or is this an optical phenomenon?

Username Protected · **Posted:** 17 Mar 2022, 21:05

Almost certainly something in the optics or CCD - maybe still to be tuned out by additional alignment.

Black holes are too small to see with an optical telescope. There was sort of an image of a black hole using an array of radio telescopes that spanned the whole globe - and its just barely detectable with lots of processing. (the dark spot is still quite a bit larger than teh actual black hole but is a result of how it bends light)

https://eventhorizontelescope.org/

Username Protected wrote:

so I zoomed in on that initial picture. it is captivating.

if you looks closely, you can see a few "rings of light." i.e., a black dot with a ring of starlight around it. could these be black holes, or is this an optical phenomenon?

James Web Telescope