On 2023-10-17, John Larkin wrote:> On Mon, 16 Oct 2023 23:24:24 -0000 (UTC), Dan Purgert <dan@djph.net> > wrote: > >>On 2023-10-16, Jeroen Belleman wrote: >>> The six-pointed stars we see in all JWST images are rather >>> disturbing, yet, it should be easy enough to filter them out. >>> Why don't they? >> >>What's wrong with the diffraction spikes from the JWST? >> >>Also, there should be 8, as I recall (although the horizontal ones are >>pretty dim, compared to the vertical and "X" shaped ones). > > Aren't the mirrors hexagons?Yes, the primary mirrors are hexagons, but the standoffs for the secondary mirror also generates a 6-pointed diffraction spike. The "X" portion just overlaps. Here's a diagram of the elements: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#/media/File:JWST_diffraction_spikes.svg -- |_|O|_| |_|_|O| Github: https://github.com/dpurgert |O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860
Six-pointed stars in JWST images
Started by ●October 16, 2023
Reply by ●October 17, 20232023-10-17
Reply by ●October 17, 20232023-10-17
The idiot Jeroen Belleman <jeroen@nospam.please> persisting in being an Off-topic troll... -- Jeroen Belleman <jeroen@nospam.please> wrote:> Path: not-for-mail > From: Jeroen Belleman <jeroen@nospam.please> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 10:43:58 +0200 > Organization: A noiseless patient Spider > Lines: 20 > Message-ID: <uglhgh$2s2a2$1@dont-email.me> > References: <ugkb50$2fie1$1@dont-email.me> > <vddriil08ukn39robf8qulploqmq8cpni8@4ax.com> > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8; format=flowed > Content-Transfer-Encoding: 7bit > Injection-Date: Tue, 17 Oct 2023 08:44:02 -0000 (UTC) > Injection-Info: dont-email.me; posting-host="b503a7b3294e248d12fc99c7171003f3"; > logging-data="3017026"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18v5PxJDsKhtPofhUwnHMxf" > User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 > Thunderbird/102.13.0 > Cancel-Lock: sha1:/UxdbKKQUGPWcAw//K4JZiCG5QI= > In-Reply-To: <vddriil08ukn39robf8qulploqmq8cpni8@4ax.com> > Content-Language: en-US > X-Received-Bytes: 1861
Reply by ●October 17, 20232023-10-17
The idiot Martin Brown <'''newspam'''@nonad.co.uk> persisting in being an Off-topic troll... -- Martin Brown <'''newspam'''@nonad.co.uk> wrote:> Path: not-for-mail > From: Martin Brown <'''newspam'''@nonad.co.uk> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 10:14:11 +0100 > Organization: A noiseless patient Spider > Lines: 57 > Message-ID: <uglj95$2sfn5$1@dont-email.me> > References: <ugkb50$2fie1$1@dont-email.me> > <vddriil08ukn39robf8qulploqmq8cpni8@4ax.com> <uglhgh$2s2a2$1@dont-email.me> > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8; format=flowed > Content-Transfer-Encoding: 7bit > Injection-Date: Tue, 17 Oct 2023 09:14:13 -0000 (UTC) > Injection-Info: dont-email.me; posting-host="9fdb9cb47956955bae9cd63b22ad64ba"; > logging-data="3030757"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19/+kNrW0S9RS1vwd4BPMgya/ek3L+o++xmVKjt7Zediw==" > User-Agent: Mozilla Thunderbird > Cancel-Lock: sha1:VsOn8YYet/tjzCr84vUN8YRSiMo= > Content-Language: en-GB > In-Reply-To: <uglhgh$2s2a2$1@dont-email.me> > X-Received-Bytes: 3722
Reply by ●October 17, 20232023-10-17
The idiot John Larkin <jl@997PotHill.com> persisting in being an Off-topic troll... -- John Larkin <jl@997PotHill.com> wrote:> Path: not-for-mail > NNTP-Posting-Date: Tue, 17 Oct 2023 02:55:29 +0000 > From: John Larkin <jl@997PotHill.com> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Mon, 16 Oct 2023 19:55:20 -0700 > Organization: Highland Tech > Reply-To: xx@yy.com > Message-ID: <tptrii9aps59kui7ionmrf6an0snh6e9r6@4ax.com> > References: <ugkb50$2fie1$1@dont-email.me> <slrnuirhjv.2f4.dan@djph.net> > X-Newsreader: Forte Agent 3.1/32.783 > MIME-Version: 1.0 > Content-Type: text/plain; charset=us-ascii > Content-Transfer-Encoding: 7bit > Lines: 15 > X-Trace: sv3-U2DsvmfZT8SIxnZgjUhvevOe8WX8gnM3EP0xoMI8v5gvgsHtbcgOPPkFXUj06yMfvafcFfLtHWciA6e!pqSDLC2edvG0RKjlL8h2TCeIlbnXOSjgXNUco9XqajTyjY4qLTcg291ZnU7+UwWLzS2GKItx/RwA!NBvncQ== > X-Complaints-To: www.supernews.com/docs/abuse.html > X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html > X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers > X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly > X-Postfilter: 1.3.40 > Bytes: 1605 > X-Received-Bytes: 1785
Reply by ●October 17, 20232023-10-17
The arsehole Dan Purgert <dan@djph.net> persisting in being an Off-topic troll... -- Dan Purgert <dan@djph.net> wrote:> Path: not-for-mail > From: Dan Purgert <dan@djph.net> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 10:48:19 -0000 (UTC) > Organization: A noiseless patient Spider > Lines: 28 > Message-ID: <slrnuispma.2f4.dan@djph.net> > References: <ugkb50$2fie1$1@dont-email.me> <slrnuirhjv.2f4.dan@djph.net> > <tptrii9aps59kui7ionmrf6an0snh6e9r6@4ax.com> > Injection-Date: Tue, 17 Oct 2023 10:48:19 -0000 (UTC) > Injection-Info: dont-email.me; posting-host="56a998beae8f1a7144fc2a6e745dfb7b"; > logging-data="3065666"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/K4T4bIXvc4VD/GrjzVas/m2FI4cAT7E8=" > User-Agent: slrn/1.0.3 (Linux) > Cancel-Lock: sha1:YT7YcPxpZMDcuDpF2AOiD3lmdbA= > X-Received-Bytes: 1958
Reply by ●October 17, 20232023-10-17
The arsehole Martin Brown <'''newspam'''@nonad.co.uk> persisting in being an Off-topic troll... -- Martin Brown <'''newspam'''@nonad.co.uk> wrote:> Path: not-for-mail > From: Martin Brown <'''newspam'''@nonad.co.uk> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 08:56:38 +0100 > Organization: A noiseless patient Spider > Lines: 73 > Message-ID: <uglenn$2rc2h$1@dont-email.me> > References: <ugkb50$2fie1$1@dont-email.me> > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8; format=flowed > Content-Transfer-Encoding: 7bit > Injection-Date: Tue, 17 Oct 2023 07:56:39 -0000 (UTC) > Injection-Info: dont-email.me; posting-host="9fdb9cb47956955bae9cd63b22ad64ba"; > logging-data="2994257"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18iMNCebRTnQXiuxeoFME9sGVcWz3BnD4+03Po2V+7l9w==" > User-Agent: Mozilla Thunderbird > Cancel-Lock: sha1:1Xn1kXmX3BafoSXrDODLipuY078= > In-Reply-To: <ugkb50$2fie1$1@dont-email.me> > Content-Language: en-GB > X-Received-Bytes: 3749
Reply by ●October 17, 20232023-10-17
On Tue, 17 Oct 2023 10:43:58 +0200, Jeroen Belleman <jeroen@nospam.please> wrote:>On 10/17/23 00:14, john larkin wrote: >> On Mon, 16 Oct 2023 23:49:17 +0200, Jeroen Belleman >> <jeroen@nospam.please> wrote: >> >>> The six-pointed stars we see in all JWST images are rather >>> disturbing, yet, it should be easy enough to filter them out. >>> Why don't they? >>> >>> Jeroen Belleman >> >> Why disturbing? >> > >I find them objectionable because they often obscure (oblude?) >nearby detail. These days, it should be relatively easy to >Fourier-transform the image, apply some window function to remove >the hexagon pattern of the mirrors and the shadows of the secondary >mirror supports, and then transform it back again. > >Jeroen BellemanNASA is basically a money-burning PR operation, and probably elects to show star patterns in pretty public pictures. And if the bright lines saturate the detector, whatever is under them can't be recovered.
Reply by ●October 17, 20232023-10-17
On 17/10/2023 14:57, John Larkin wrote:> On Tue, 17 Oct 2023 10:43:58 +0200, Jeroen Belleman > <jeroen@nospam.please> wrote: > >> On 10/17/23 00:14, john larkin wrote: >>> On Mon, 16 Oct 2023 23:49:17 +0200, Jeroen Belleman >>> <jeroen@nospam.please> wrote: >>> >>>> The six-pointed stars we see in all JWST images are rather >>>> disturbing, yet, it should be easy enough to filter them out. >>>> Why don't they? >>>> >>>> Jeroen Belleman >>> >>> Why disturbing? >>> >> >> I find them objectionable because they often obscure (oblude?) >> nearby detail. These days, it should be relatively easy to >> Fourier-transform the image, apply some window function to remove >> the hexagon pattern of the mirrors and the shadows of the secondary >> mirror supports, and then transform it back again. >> >> Jeroen Belleman > > NASA is basically a money-burning PR operation, and probably elects to > show star patterns in pretty public pictures.It is the other way around. The star pattern is a diffraction effect from the physical shape of the aperture which was made up of hexagons so that it could fold up into a tight cylindrical space for launch. It was news to me that JWST was named after a controversial NASA manager - I had initially thought it had been named after one of my fellow countrymen - the Victoria amateur astronomer Rev Thomas Webb whose name lives on in a society for the study of deep sky objects. He wrote one of the first major work on such objects (amateur and professional astronomy was quite blurred back then). https://www.webbdeepsky.com/wbg/twwebb.html Messier's name also lives on with his catalogue of 106+/-4 catalogue of nuisance fuzzy objects when comet hunting. He tended to be drunk when making observational notes so some of his objects are disputed. ISTR 102 of them are now fairly certain and the others are later additions.> And if the bright lines saturate the detector, whatever is under them > can't be recovered.It is true that whatever was under a diffraction spike is difficult to recover. But you can't blame NASA for that - the laws of physics play an important part in determining what a telescope can actually see. There are stars that are too bright for the JWST to observe. If anything ever saturates a detector it is actually the unresolved point object that is at the centre of the diffraction pattern. When that happens you get readout bleed along a column of cells. You sometimes see it in the realtime preview of a phone being used as a camera when there are bright lights in a dim scene. The wells in the tiny chips are not very deep so very easily saturate. -- Martin Brown
Reply by ●October 17, 20232023-10-17
The arsehole John Larkin <jl@997PotHill.com> persisting in being an Off-topic troll... -- John Larkin <jl@997PotHill.com> wrote:> Path: not-for-mail > NNTP-Posting-Date: Tue, 17 Oct 2023 13:57:10 +0000 > From: John Larkin <jl@997PotHill.com> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 06:57:00 -0700 > Organization: Highland Tech > Reply-To: xx@yy.com > Message-ID: <8g4tiihlpsrmaup15koqi70m9jse6op4nm@4ax.com> > References: <ugkb50$2fie1$1@dont-email.me> <vddriil08ukn39robf8qulploqmq8cpni8@4ax.com> <uglhgh$2s2a2$1@dont-email.me> > X-Newsreader: Forte Agent 3.1/32.783 > MIME-Version: 1.0 > Content-Type: text/plain; charset=us-ascii > Content-Transfer-Encoding: 7bit > Lines: 30 > X-Trace: sv3-tvaXG74do273VqFDy0Q0sJIYuQPN5ua8sUDcpTvdc9KQwJhhBlKdMLNZulhlwEFK60Md8zvdVvXeIkw!nPiq+sC/MgOxiNjK0qjnPmMNdJNVF+bX81afB6GTPSnGbH2ig+vQC3BYhj9GfopN6eJXdTqcq0QV!aa/Mww== > X-Complaints-To: www.supernews.com/docs/abuse.html > X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html > X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers > X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly > X-Postfilter: 1.3.40 > X-Received-Bytes: 2358
Reply by ●October 17, 20232023-10-17
The arsehole Martin Brown <'''newspam'''@nonad.co.uk> persisting in being an Off-topic troll... -- Martin Brown <'''newspam'''@nonad.co.uk> wrote:> Path: not-for-mail > From: Martin Brown <'''newspam'''@nonad.co.uk> > Newsgroups: sci.electronics.design > Subject: Re: Six-pointed stars in JWST images > Date: Tue, 17 Oct 2023 15:35:16 +0100 > Organization: A noiseless patient Spider > Lines: 68 > Message-ID: <ugm636$30u8h$1@dont-email.me> > References: <ugkb50$2fie1$1@dont-email.me> <vddriil08ukn39robf8qulploqmq8cpni8@4ax.com> <uglhgh$2s2a2$1@dont-email.me> <8g4tiihlpsrmaup15koqi70m9jse6op4nm@4ax.com> > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8; format=flowed > Content-Transfer-Encoding: 7bit > Injection-Date: Tue, 17 Oct 2023 14:35:18 -0000 (UTC) > Injection-Info: dont-email.me; posting-host="9fdb9cb47956955bae9cd63b22ad64ba"; logging-data="3176721"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19qtiHGapiHCPphzsebloFOdC51pUsVtRWH2mBzm6DM8g==" > User-Agent: Mozilla Thunderbird > Cancel-Lock: sha1:QHYipFkjC+tQSg3DgxcI5RWNlx4= > Content-Language: en-GB > In-Reply-To: <8g4tiihlpsrmaup15koqi70m9jse6op4nm@4ax.com> > X-Received-Bytes: 3935
