banner
banner

28 Mar 2024, 22:04 [ UTC - 5; DST ]


Concorde Battery (banner)



Reply to topic  [ 423 posts ]  Go to page Previous  1 ... 14, 15, 16, 17, 18, 19, 20 ... 29  Next
Username Protected Message
 Post subject: Re: James Web Telescope
PostPosted: 17 Mar 2022, 22:45 
Offline


User avatar
 Profile




Joined: 02/10/12
Posts: 6819
Post Likes: +7927
Company: Minister of Pith
Location: Florida
Aircraft: Piper PA28/140
Username Protected wrote:
It'd be nice if they could get rid of the horrendous lens flare.

Freaking JJ Abrams....

_________________
"No comment until the time limit is up."


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 03:48 
Online


User avatar
 WWW  Profile




Joined: 02/08/08
Posts: 5486
Post Likes: +3505
Location: Seattle
Aircraft: A36
Here's a detailed discussion of the telescope's deployment and testing so far.

For additional explanation of the diffraction of the image of the target star, skip to 28:12.

The video also includes discussion of the some of the instruments, which are still being cooled and calibrated.

[youtube]https://youtu.be/BgDtJYoQ3ks[/youtube]

_________________
-Bruce
bruceair.wordpress.com
youtube.com/@BruceAirFlying


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 18:15 
Offline



User avatar
 Profile




Joined: 04/26/13
Posts: 19767
Post Likes: +19433
Location: Columbus , IN (KBAK)
Aircraft: 1968 Baron D55
I wish someone would answer the diffraction question in more detail. I don’t care what causes it, to me it looks like a distortion that ruins the image. Tell me why that isn’t so. I have to assume that the lack of concern by those involved indicates that it isn’t, but that alone doesn’t satisfy my curiosity.

_________________
My last name rhymes with 'geese'.


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 18:25 
Offline


User avatar
 WWW  Profile




Joined: 11/30/12
Posts: 4006
Post Likes: +4410
Location: Santa Fe, NM (KSAF)
Aircraft: B200, 500B
Username Protected wrote:
I wish someone would answer the diffraction question in more detail. I don’t care what causes it, to me it looks like a distortion that ruins the image. Tell me why that isn’t so. I have to assume that the lack of concern by those involved indicates that it isn’t, but that alone doesn’t satisfy my curiosity.

"The process will essentially create an image of 18 random, blurry points of light. For the first few weeks of mirror alignment, the team will keep the instrument trained on the star while they make microscopic adjustments to the mirror segments; ultimately that collection of 18 blurry dots will become a focused image of a single star."

_________________
Be Nice


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 18:27 
Offline



User avatar
 Profile




Joined: 04/26/13
Posts: 19767
Post Likes: +19433
Location: Columbus , IN (KBAK)
Aircraft: 1968 Baron D55
Username Protected wrote:
I wish someone would answer the diffraction question in more detail. I don’t care what causes it, to me it looks like a distortion that ruins the image. Tell me why that isn’t so. I have to assume that the lack of concern by those involved indicates that it isn’t, but that alone doesn’t satisfy my curiosity.

"The process will essentially create an image of 18 random, blurry points of light. For the first few weeks of mirror alignment, the team will keep the instrument trained on the star while they make microscopic adjustments to the mirror segments; ultimately that collection of 18 blurry dots will become a focused image of a single star."

They’ve already done that. They now have a single image of a single star with lens flare spikes coming out of it.
_________________
My last name rhymes with 'geese'.


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 19:15 
Offline


User avatar
 WWW  Profile




Joined: 11/30/12
Posts: 4006
Post Likes: +4410
Location: Santa Fe, NM (KSAF)
Aircraft: B200, 500B
Username Protected wrote:
They’ve already done that. They now have a single image of a single star with lens flare spikes coming out of it.

The alignment status is still listed as "ongoing."

_________________
Be Nice


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 19:24 
Offline


User avatar
 Profile




Joined: 07/06/14
Posts: 2978
Post Likes: +1967
Location: MA
Aircraft: Cessna 340A
Username Protected wrote:
They’ve already done that. They now have a single image of a single star with lens flare spikes coming out of it.

The alignment status is still listed as "ongoing."

Right, I read that as they continue alignment the diffraction pattern will get narrower and dimmer. Also, it seems this is a function of looking at a relatively bright object, probably closer / brighter than you would normally use this instrument for.

Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 19:35 
Online


User avatar
 WWW  Profile




Joined: 02/08/08
Posts: 5486
Post Likes: +3505
Location: Seattle
Aircraft: A36
A rough transcript from the video:

"Any telescope that has special structures like the shape of our mirrors will have that kind of spikes in it. Those are actually the result, in this case, of having hexagonal segments...and we also have our struts, the things that hold our secondary mirror up, and because of the way light travels, that causes something called diffraction that makes those spikes. You see that most intensely when you have a very bright star...."

_________________
-Bruce
bruceair.wordpress.com
youtube.com/@BruceAirFlying


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 21:16 
Offline




User avatar
 Profile




Joined: 12/10/07
Posts: 30426
Post Likes: +10535
Location: Minneapolis, MN (KFCM)
Aircraft: 1970 Baron B55
Username Protected wrote:
A rough transcript from the video:

"Any telescope that has special structures like the shape of our mirrors will have that kind of spikes in it. Those are actually the result, in this case, of having hexagonal segments...and we also have our struts, the things that hold our secondary mirror up, and because of the way light travels, that causes something called diffraction that makes those spikes. You see that most intensely when you have a very bright star...."

It's hard to tell from the image presented but the intensity of those sidelobe artifacts is far lower than the center of the star's image. They're also likely predictable and repeatable which means they could be eliminated with post processing if desired but in the case of mirror alignment, they are probably quite useful in their own right.

Also keep in mind that the goal of this telescope isn't the generation of pretty images but rather measuring the spectral content and brightness of distant objects. For that objective predictable diffraction effects won't be a hindrance.

_________________
-lance

It's easier to fool people than to convince them that they have been fooled.


Top

 Post subject: Re: James Web Telescope
PostPosted: 22 Mar 2022, 21:31 
Offline



User avatar
 Profile




Joined: 04/26/13
Posts: 19767
Post Likes: +19433
Location: Columbus , IN (KBAK)
Aircraft: 1968 Baron D55
Username Protected wrote:
It's hard to tell from the image presented but the intensity of those sidelobe artifacts is far lower than the center of the star's image. They're also likely predictable and repeatable which means they could be eliminated with post processing if desired but in the case of mirror alignment, they are probably quite useful in their own right.

Also keep in mind that the goal of this telescope isn't the generation of pretty images but rather measuring the spectral content and brightness of distant objects. For that objective predictable diffraction effects won't be a hindrance.

Now that’s the kind of answer I was looking for. Thanks Lance.

_________________
My last name rhymes with 'geese'.


Top

 Post subject: Re: James Web Telescope
PostPosted: 23 Mar 2022, 03:02 
Offline


User avatar
 WWW  Profile




Joined: 05/11/10
Posts: 9260
Post Likes: +11837
Company: ? Most always. I like people.
Location: KFIN Flagler, FL
Aircraft: 1991 Bonanza A36
It seems that a bright object is not required for the spikes to be generated. Click on the picture and zoom in on the tiny points of light. Each has the same spiked image.

_________________
Bible In Poems
BibleInPoems.com

BNice


Top

 Post subject: Re: James Web Telescope
PostPosted: 23 Mar 2022, 09:04 
Online


User avatar
 WWW  Profile




Joined: 02/08/08
Posts: 5486
Post Likes: +3505
Location: Seattle
Aircraft: A36
Diffraction isn't always a "bug"--e.g., it's the basis of X-ray crystallography. See also Photo 51.

_________________
-Bruce
bruceair.wordpress.com
youtube.com/@BruceAirFlying


Top

 Post subject: Re: James Web Telescope
PostPosted: 23 Mar 2022, 11:40 
Offline




User avatar
 Profile




Joined: 12/10/07
Posts: 30426
Post Likes: +10535
Location: Minneapolis, MN (KFCM)
Aircraft: 1970 Baron B55
Username Protected wrote:
It seems that a bright object is not required for the spikes to be generated. Click on the picture and zoom in on the tiny points of light. Each has the same spiked image.

The same pattern will exist for every point of light in the sky but the relative intensity of the spikes to the actual object should remain constant.

_________________
-lance

It's easier to fool people than to convince them that they have been fooled.


Top

 Post subject: Re: James Web Telescope
PostPosted: 24 Mar 2022, 06:32 
Offline



User avatar
 Profile




Joined: 04/26/13
Posts: 19767
Post Likes: +19433
Location: Columbus , IN (KBAK)
Aircraft: 1968 Baron D55
So, then how is that not a problem when you are trying to observe distant objects with as much resolution as possible?

_________________
My last name rhymes with 'geese'.


Top

 Post subject: Re: James Web Telescope
PostPosted: 24 Mar 2022, 11:14 
Offline




User avatar
 Profile




Joined: 12/10/07
Posts: 30426
Post Likes: +10535
Location: Minneapolis, MN (KFCM)
Aircraft: 1970 Baron B55
Username Protected wrote:
So, then how is that not a problem when you are trying to observe distant objects with as much resolution as possible?

That depends on what you're trying to observe about those distant objects. You can still measure their size, brightness, spectrum, relative motion, doppler shift, and a bunch of things I don't remember. If you were trying to count the number of craters on a planet circling a star a few million light years away those image artifacts might make that impossible or at least more difficult but that's not what JW is about. It doesn't even have an imaging camera that can record "visible" light.

_________________
-lance

It's easier to fool people than to convince them that they have been fooled.


Top

Display posts from previous:  Sort by  
Reply to topic  [ 423 posts ]  Go to page Previous  1 ... 14, 15, 16, 17, 18, 19, 20 ... 29  Next




You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  

Terms of Service | Forum FAQ | Contact Us

BeechTalk, LLC is the quintessential Beechcraft Owners & Pilots Group providing a forum for the discussion of technical, practical, and entertaining issues relating to all Beech aircraft. These include the Bonanza (both V-tail and straight-tail models), Baron, Debonair, Duke, Twin Bonanza, King Air, Sierra, Skipper, Sport, Sundowner, Musketeer, Travel Air, Starship, Queen Air, BeechJet, and Premier lines of airplanes, turboprops, and turbojets.

BeechTalk, LLC is not affiliated or endorsed by the Beechcraft Corporation, its subsidiaries, or affiliates. Beechcraft™, King Air™, and Travel Air™ are the registered trademarks of the Beechcraft Corporation.

Copyright© BeechTalk, LLC 2007-2024

.headsetsetc_Small_85x50.jpg.
.aircraftferry-85x50.jpg.
.planelogix-85x100-2015-04-15.jpg.
.ssv-85x50-2023-12-17.jpg.
.geebee-85x50.jpg.
.kingairnation-85x50.png.
.Wentworth_85x100.JPG.
.Wingman 85x50.png.
.kingairacademy-85x100.png.
.aeroled-85x50-2022-12-06.jpg.
.shortnnumbers-85x100.png.
.AAI.jpg.
.traceaviation-85x150.png.
.aircraftassociates-85x50.png.
.avionwealth-85x50.png.
.boomerang-85x50-2023-12-17.png.
.midwest2.jpg.
.dbm.jpg.
.aviationdesigndouble.jpg.
.pure-medical-85x150.png.
.CiESVer2.jpg.
.bpt-85x50-2019-07-27.jpg.
.daytona.jpg.
.stanmusikame-85x50.jpg.
.Latitude.jpg.
.bullardaviation-85x50-2.jpg.
.sierratrax-85x50.png.
.saint-85x50.jpg.
.cav-85x50.jpg.
.blackwell-85x50.png.
.temple-85x100-2015-02-23.jpg.
.tat-85x100.png.
.jetacq-85x50.jpg.
.gallagher_85x50.jpg.
.camguard.jpg.
.centex-85x50.jpg.
.pdi-85x50.jpg.
.blackhawk-85x100-2019-09-25.jpg.
.Foreflight_85x50_color.png.
.SCA.jpg.
.lucysaviation-85x50.png.
.kadex-85x50.jpg.
.tempest.jpg.
.concorde.jpg.
.Rocky-Mountain-Turbine-85x100.jpg.
.Marsh.jpg.
.wilco-85x100.png.
.wat-85x50.jpg.
.avfab-85x50-2018-12-04.png.
.chairmanaviation-85x50.jpg.
.airmart-85x150.png.
.MountainAirframe.jpg.
.ABS-85x100.jpg.
.one-mile-up-85x100.png.
.Genesys_85x50.jpg.
.ei-85x150.jpg.
.jandsaviation-85x50.jpg.