[HN Gopher] 2.7-meters Telescope mirror shot 7 times (1970)
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2.7-meters Telescope mirror shot 7 times (1970)
Author : jeanlucas
Score : 191 points
Date : 2024-09-05 18:19 UTC (4 days ago)
(HTM) web link (www.cbat.eps.harvard.edu)
(TXT) w3m dump (www.cbat.eps.harvard.edu)
| jeanlucas wrote:
| This is no news by any metric, but I found curious that:
|
| 1. It only reduced the telescope efficiency by 1%
|
| 2. The original report from 1970 is still up!
|
| This is the video that made me aware of the incident:
| https://www.youtube.com/watch?v=59cw_bDbEqA
| worstspotgain wrote:
| To be fair, it's Texas. Even the state motto is 1% riddled with
| bullet holes.
| pmb wrote:
| The state motto of Texas is "Friendship".
|
| (this is true)
| worstspotgain wrote:
| If it was Friendship before the Alamo I'd say that works
| out about right.
| lb1lf wrote:
| ...whereas that of New Hampshire is 'Live free or die'
|
| Incidentally, NH licence plates are stamped out by prison
| inmates.
|
| Now THAT is cruel and unusual punishment, right there!
|
| Edit: For those not well versed in NH plates, the state
| motto is embossed on each and every number plate. (This may
| be the case for every US state, for all I know)
| tialaramex wrote:
| > This may be the case for every US state, for all I know
|
| Nope. What the jurisdictions choose to write on plates
| varies, often for a fee you can have something different,
| either of your choice (within limits) or from some
| limited selection.
|
| Famously DC has plates quipping about the "Taxation
| Without Representation" which was notionally the reason
| the United States wanted independence. The District of
| Columbia of course does pay federal taxes but does not
| receive proper democratic representation in exchange,
| exactly the situation the colonists complained of and
| with exactly the same retort offered in response+.
|
| [This is a very small hypocrisy compared to say declaring
| that "All men shall be free" and continuing to literally
| enslave some of them for example]
|
| + The Congress insists, just like the Westminster
| Parliament, that these tax payers _are_ represented, but
| virtually, with the entire institution actually somehow
| representing their interests. If this strikes you as
| poppycock for Westminster, it should feel no different
| closer to home.
| eadmund wrote:
| It seems to me that it makes a great deal of sense for
| the seat of the federal government to be located in a
| federal district independent of any state's control. It
| also would not make sense for that federal district to be
| represented as a state -- that would end up being a
| circular dependency, since the federal government is
| created _by_ the states, and it doesn't make sense for
| the federal district to participate in creating and
| sustaining itself.
|
| Those who choose to live within the federal district have
| a privilege others in the United States do not have:
| direct physical interaction with and influence over the
| individuals composing the federal government. It makes
| sense to me that the privilege is balanced with a lack of
| representation in the Senate and House. Note that they
| _do_ have representation in the Electoral College.
|
| It also makes sense to me to retrocede the majority of
| the current federal district back to the state of
| Maryland.
| mhb wrote:
| And, incidentally, you can choose to cover or remove the
| motto on your plate:
| https://news.ycombinator.com/item?id=41488122
| dmoy wrote:
| On the subject of bullet holes in 1% of the thing, NH
| also has way laxer gun laws than Texas. (Or at least had
| laxer laws 5 years ago, I suppose Texas probably has
| loosened gun laws in recent years)
|
| No permit for carrying, no duty to inform, no "no guns"
| signs for buildings that carry any legal weight beyond
| trespass. NH allows guns in bars, Texas does not. NH you
| can still protest with guns, which is rare in most states
| after the 1960s era civil rights protests with guns.
| Texas nominally prohibits carrying guns for 5 yrs after a
| violent offense, NH does not. Etc etc.
| lazide wrote:
| Yeah, Texas has been all hat no cattle for a long time
| re: guns. Still looser restrictions than California
| though.
|
| If you want real 'wild west' living, the closest you'll
| come is Nevada (except for Clark County), Wyoming (except
| for Jackson), and Alaska (except for Anchorage). A few
| other places too.
| 404mm wrote:
| You know the news is from 1970 because back then there was a
| mental institution for people like him. And it's not like we
| have fewer issues now.
| dghughes wrote:
| Yeah that stood out. There's basically zero mental health
| resources now after Reagan gutted it. Now the shooter would
| himself be shot or thrown in jail only to come out worse.
| Repeat.
| WarOnPrivacy wrote:
| Between genealogy and caring for a MI spouse, I learned it
| went down like this.
|
| Late 18th to early 19th c. people with compassion and
| insight opened sanitariums to provide care for folks with
| brain disorders. Much of the care was truly revolutionary
| and helpful. Some of it was other things. The public was
| impressed and inspired.
|
| The founders died off and institutions continued on without
| their vision. The public lost interest; funds waned but
| need did not.
|
| By the 1980s institutions were no longer safe or caring.
| The public had moved on. Few in power knew or cared.
|
| Politicians saw funding streams they could grab w/o risking
| reelection and forced our MI population into homelessness.
|
| We're still there. My 5 state institutions are dangerous
| hellholes. Homeless are everywhere here.
|
| source: w/o long-term inpatient care, wife left the family
| to become homeless
| TremendousJudge wrote:
| I completely agree that mental institutions are important
| and need more funding/attention. However, your comment
| implies that all homeless people have mental problems
| that need treatment. Many are just very poor and most of
| their problems (mental or otherwise) are
| caused/exacerbated by homelessness itself. I consider
| myself sane but if I didn't have a permanent shelter and
| had to face the streets every night I'd go crazy too
| samatman wrote:
| It implies nothing of the sort. What it _states_ ,
| without making implications, is that the very mentally
| ill who would otherwise be in institutions, are instead
| homeless. Which is the case.
| TremendousJudge wrote:
| This sentence:
|
| >We're still there. My 5 state institutions are dangerous
| hellholes. Homeless are everywhere here.
|
| Implies that "Homeless are everywhere here" wouldn't be
| the case if the institutions were good. I disagree. I
| believe that if the institutions were good there would
| still be homeless people, unless somebody declares to be
| living on the streets to be a mental condition that
| warrants forced institutionalization.
| sangnoir wrote:
| A->B =/= B->A.
|
| OPs view is that lack of MI (A) results in homelessness
| (B). You're taking that further and making the argument
| that the existence of homelessness (B) implies lack of
| good institutions (A) - an argument OP didn't make.
| SoftTalker wrote:
| A mental institution in Texas in 1970 was likely quite
| undifferentiated from a prison, and one that you could be
| sent to without having been convicted of anything. Just
| needed a state-employed doctor to declare you insane.
| tjpnz wrote:
| Watched this last night and had a chuckle at how his initial
| attempt to damage it failed - hammer flew right off the
| surface. Also how seemingly nonchalant they were about the
| event.
| eternauta3k wrote:
| 7 10 cm diameter circles have 1% of the area of a 2.7m diameter
| circle.
| avidiax wrote:
| Reminds me of the article from Lensrentals about how much front
| element scratches affect photo quality. Apparently not very much.
|
| Wait, did they say scratches? They meant a completely cracked
| front element.
|
| https://www.lensrentals.com/blog/2008/10/front-element-scrat...
| Zobat wrote:
| "tis but a scratch".
| krackers wrote:
| Given that, why are specs of dust on glasses so noticeable?
| consp wrote:
| Never notice them, only big stains. Maybe it depends on the
| strength and type?
| qq66 wrote:
| Your eyes are a "wide angle lens." Scratches on wide angle
| lenses are also very noticeable
| imhoguy wrote:
| Or damn eye floaters.
| left-struck wrote:
| Like with scratches on lenses, those floaters are only
| visible when your eyes have a small aperture, like when
| you're outside in broad daylight
| wkat4242 wrote:
| Floaters are a bit different because they are behind the
| lens. It's more comparable with dust on the sensor in an
| SLR (or dust in the sensor cavity)
|
| That is also more noticeable with lower aperture but for
| a different reason. With a low aperture the light comes
| more from a single direction so the shadow from the dust
| particles is more defined. The same happens with the
| floaters. The reason you only see them when looking at
| the sky is because they're pretty transparent and you
| need a bright detailless surface to see the low contrast
| they provide.
|
| But it's very different from scratches on a lens surface
| because those are in front of the optics.
| philjohn wrote:
| I'd love to get rid of mine ... and there is a procedure,
| but I looked up photos of it and ... nope. Think I'll
| just stick to using dark mode when using my computer
| instead.
| ridgeguy wrote:
| Can you share a link to that procedure? I have floaters
| bad enough to make me consider drastic steps.
| throwanem wrote:
| Talking to an optometrist isn't usually that drastic.
| pasc1878 wrote:
| All the ones I talk to say there is no way to fix
| floaters.
|
| Thus a link to the process would be useful - even if
| searching for reviews of that process would show it does
| not work.
| xattt wrote:
| Vitrectomy would be what you are looking for. It's fairly
| drastic as you are pulling vitreous humour from the eye
| in order to get rid of the floaters.
| jcims wrote:
| There's also laser vitreolysis that's substantially less
| invasive.
|
| I'm sure there are more authoritative links but i picked
| this one because i thought it said 'burningeye.com' at
| first:
|
| https://www.brueningeye.com/laser-floater-removal
| throwanem wrote:
| During my last eye exam my optometrist advised me to call
| the office in case of a sudden increase in floaters,
| which might warn of a condition common in the myopic and
| potentially progressing to retinal detachment, but which
| can be easily treated during an office visit by a process
| I understood to involve lasers.
|
| I didn't name the procedure because, not yet having
| needed to study it, I don't know what it is called. (I
| don't recall the proper name of the floater-producing,
| dangerous but ameliorable condition, either.) But I
| understood its intent to be preventing any risk of
| progressive loss of vision, rather than removing the
| floaters directly. Maybe we're talking about two
| different things, though.
| seszett wrote:
| But they aren't, only dust on the sensor is noticeable, dust
| anywhere else just softens the image somewhat (unless maybe
| stopped all the way down with some lenses, but it would be
| unusual).
|
| _Edit_ heh, I was thinking about "lens glasses". I don't
| find dust on eyeglasses very noticeable unless light catches
| it in some particular way.
| Ylpertnodi wrote:
| Working with a few US, it took me a while to appreciate
| "eye-glasses", as a thing (noun). TIL "lens glasses", is
| also a thing. I was rather hoping context would imply what
| the subject matter is.
| throwway120385 wrote:
| Also distinguished from "opera glasses" or "field
| glasses."
| gattr wrote:
| Similarly, you normally don't see any imperfections/dust
| specks on your cornea - but you will if you look into a
| very narrow (0.1-0.2 mm) beam of light (e.g., when using a
| telescope pushed to a very high magnification = very small
| exit pupil [1]).
|
| [1] https://en.wikipedia.org/wiki/Exit_pupil
| looofooo0 wrote:
| It is in the Fourier domain or just non sharp where the dust
| is.
| 7373737373 wrote:
| if only there was a lens that could ignore dust this way...
| porphyra wrote:
| they also have a blog post about a big house fly that somehow
| got inside the lens but did not affect image quality
| exitb wrote:
| I was once with a group at a small local observatory, trying to
| take a look at Venus, low over the horizon. As the rotating
| roof rolled into the correct position, it turned out that a
| Yagi-style antenna mounted outside sat right in middle of the
| view. It seemed like something that'd ruin your day (or night),
| but it turned out that it really made no noticeable difference.
| ajb wrote:
| I guess it's just down to the percentage of the aperture that
| is blocked?
|
| There's an amusing picture where a large owl has blocked a
| substantial portion of the view:
|
| https://apod.nasa.gov/apod/ap030401.html
| exitb wrote:
| Yes. Given enough distance, the obstructing object will
| start to come into focus, but if it's close, it just
| darkens the image. After all reflecting telescopes have a
| secondary mirror (along with its mount) permanently
| obstructing part of the primary mirror.
| DoctorOetker wrote:
| This was not a telescope, it was an all sky camera, the
| caption explicitly states the owl scratched the optics
| with its claws.
| magicalhippo wrote:
| Guess if you were imaging a bright star you'd might get some
| interesting diffraction spikes[1] though.
|
| [1]: https://en.wikipedia.org/wiki/Diffraction_spike
| madaxe_again wrote:
| You have to block a significant chunk of aperture to get
| them.
|
| This is useful, however, for focussing using a bahtinov
| mask.
|
| https://en.m.wikipedia.org/wiki/Bahtinov_mask
| skhr0680 wrote:
| Cracks, scratches, dust, fungus, and haze are all invisible
| until you shoot a photo with strong light in it. It's mentioned
| and shown in the article.
| SoftTalker wrote:
| It's like driving at night with a dirty windshield. You don't
| really notice until you meet an oncoming car with bright
| headlights. Or similar in the daytime, when you're driving
| into the sun.
| globalise83 wrote:
| Cool. I first learnt about this property when I took my first
| proper camera with zoom lens to a zoo and was able to take
| really nice pictures of a squirrel behind some kind of mesh
| enclosure. the mesh totally disappeared.
| WarOnPrivacy wrote:
| A 1970 historical image:
| https://historicimages.com/cdn/shop/products/nex48799_1200x....
| Leo_Verto wrote:
| Besides the report on mirror damage this telegram also appears to
| contain observations of "periodic comet Curmumov-Gerasimenko",
| which had been discovered a year earlier, and happens to be the
| one ESA's Rosetta mission visited in 2016.
| Mistletoe wrote:
| https://astroanecdotes.com/2015/03/26/the-mcdonald-gun-shoot...
|
| If you would like to see the bullet holes. Bigger than I imagined
| based on the telegram.
| dwighttk wrote:
| As a Cub Scout we went on a tour of the observatory and I think
| we were able to see the pictured view, but I may just be
| remembering the story and imagining the image.
|
| They definitely told us the story and all the kids were like
| "coool!"
| lexicality wrote:
| > When the sheriff arrived, the employee was arrested and later
| committed to a mental health institution. In the report
| following the incident, the sheriff, clearly being unfamiliar
| with telescope designs, stated that the mirror had indeed been
| destroyed as it had a big, circular hole, right in the middle!
|
| "no sir, that bigger hole was there before the incident... yes
| sir, it is supposed to be there"
| mnky9800n wrote:
| I wish there was more information about why the guy shot the
| telescope. But so far I find nothing.
| bovermyer wrote:
| You could try contacting the university to see who worked there
| at the time. Dr. Smith, mentioned in the article, died in 1991.
| His obituary is here:
| https://quasar.as.utexas.edu/BillInfo/HJSmithObits.html
|
| Alternatively, you could try contacting the sheriff's office in
| Austin to see if their records include a mention of the
| incident, but that information is probably protected.
| throwanem wrote:
| Once ages ago I heard a story like this, itself not young at
| time of telling, from a professor of physics. That story might
| have been set in Texas and did involve a handgun being fired
| into a telescope mirror which was not meaningfully damaged by
| the experience, but had it as a revolver wielded by a
| revivalist-type preacher who smuggled the weapon in during a
| tour to redress what he saw as a violation of God's domain.
|
| It's been ages since I was in touch with the fellow who told
| the story, so I can't immediately confirm whether these were
| the same events. But the similarities are striking.
| helsinkiandrew wrote:
| New York Times:
| https://www.nytimes.com/1970/02/07/archives/texas-man-fires-...
|
| > An employe of the Mc Donald Observatory, described as drunk by
| the sheriff and as mentally depressed by his superiors
|
| > Sheriff W. B. Medley said that the shots "completely de stroyed
| the telescope -- it was ruined." University of Texas astronomers
| in Austin said the damage was minor.
| WarOnPrivacy wrote:
| > Sheriff: Drunk suspect destroyed telescope
|
| > People who know better: Depressed employee did some minor
| damage
|
| Modern LEO techniques seem to have history.
| gcanyon wrote:
| The telescope is still in use today, and Wikipedia says that the
| damage effectively reduced the telescope from a 107 inch mirror
| to a 106 inch mirror.
|
| https://en.wikipedia.org/wiki/Harlan_J._Smith_Telescope
| alt227 wrote:
| The article itself says:
|
| "The damage is limited to small craters about 3 to 5cm in
| radius, which reduce the light collecting efficiency by about 1
| percent"
| mrb wrote:
| Here is a pic showing the bullet holes in the mirror:
| https://starhopper.org/2020/11/19/a-telescope-with-bullet-ho...
| Rinzler89 wrote:
| How did the mirror not just shatter though?
| dredmorbius wrote:
| The mirror (third largest in the world at the time) is
| composed of fused silica. Apparently manufactured in
| segments, then joined. The cooling process itself took two
| years. That's described in one of the linked YouTube videos
| in this thread:
| <https://news.ycombinator.com/item?id=41459171>
|
| The result is a glass that's remarkably immune to shattering.
| Possibly similar to a Prince Rupert's Drop, though that's my
| own speculation.
|
| <https://en.wikipedia.org/wiki/Fused_quartz>
| adolph wrote:
| Given years long cooling process (aka annealing), the
| mirror would be the opposite of a Prince Rupert's Drop,
| which is created by quenching the glass very quickly,
| similar to the process known as tempering.
|
| https://en.wikipedia.org/wiki/Annealing_(glass)
|
| https://en.wikipedia.org/wiki/Tempered_glass
| dredmorbius wrote:
| "Possibly" is doing some heavy lifting in my comment.
|
| The similarity is in the end result, not, obviously, the
| fabrication process.
|
| The strength of the Prince Rupert's Drop comes from the
| differential tensions and stresses in the head-end of the
| drop. The tail, of course, is remarkably fragile and will
| lead to the explosive failure of the entire drop. The
| head can withstand hammer and even bullet impacts, as
| Destin Sandlin has demonstrated multiple times on his
| "Smarter Every Day" YouTube channel. I'd suspect a
| similar tensile arrangement in fused silica, though of
| course I may be wrong on that.
| alwa wrote:
| Isn't the original cooling process you're describing
| "annealing," by which glasses are cooled slowly so as to
| allow internal tensions to equalize? A task requiring
| exponentially more time as the size of the slab of glass
| increases?
|
| I seem to remember glassmakers using a device called a
| polariscope to actually see those internal stresses [0].
| Which makes me wonder if there are optical considerations
| as well as physical ones--although I guess if the whole
| thing is getting silvered, probably not.
|
| My understanding, which could be flawed, was that
| perfectly annealed glass resists cracking because there
| isn't a clear fault line to cleave across, something akin
| to the way hot water in a perfectly smooth glass has
| trouble boiling if deprived of a nucleation site. While a
| Rupert's drop achieves its stability by something more
| akin to the trope of a "Mexican standoff," [1], where
| countervailing tensions are so densely frozen in place
| that a little extra tension from the outside makes little
| difference (but when one crack forms, all bets are off
| and the tensions resolve explosively).
|
| I'm also reminded of one of my very favorite moments of
| video: the silvering pass during the manufacture of the
| Rubin Observatory's 23.5-ton, 8.4-meter-diameter mirror;
| which took from 2008 until 2019 to manufacture:
|
| https://m.youtube.com/watch?v=ftKsP3do4nM&t=38
|
| [0]
| https://www.public.asu.edu/~aomdw/GSI/Glass_Strain.html
|
| [1] https://www.backstage.com/magazine/article/how-to-do-
| a-mexic...
| dredmorbius wrote:
| I'm well out of my depth, so, at this point, I don't
| know.
| klyrs wrote:
| According to TFA, they're craters, not proper holes. The
| force of the bullet wasn't enough to puncture the glass, just
| puverize the points of impact
| hooper wrote:
| Part of this that hasn't been mentioned is that the mirror is
| thicker than you might expect. The observatory's website says
| 12.5 inches (though it will vary somewhat across the curved
| surface).
| MeteorMarc wrote:
| Proven to be vandalproof!
| moffkalast wrote:
| > McDonald Observatory, University of Texas
|
| And all right in the world.
| geocrasher wrote:
| Last year I built a Hadley telescope, which is a 3d printed
| structure with some inexpensive optics from China.
|
| https://www.printables.com/model/224383-astronomical-telesco...
|
| One of the things that surprised me, being new to telescopes (and
| certainly never having built one) was that it was deemed better
| to leave dust on the optics than to potentially damage them by
| trying to clean them. The dust just doesn't affect image quality.
|
| I had no ide athat would scale up to gunshots however! Very
| impressive.
| verandaguy wrote:
| I say this having read the mailing list and specifically the part
| that mentions the mirror is made of fused silica:
|
| What the _hell_ is that mirror made of?
|
| Is this kind of behaviour a well-documented/practical property of
| silica? I would assume that it'd shatter after _any_ amount of
| shots and a hammer blow.
| throwway120385 wrote:
| Fused silica is very pure quartz.
| verandaguy wrote:
| Wouldn't that be quite brittle, though?
| lazide wrote:
| It Depends(tm). Usually on the grain alignment/lack
| thereof. As long as the grains are suitably randomized, it
| can be very durable.
| [https://en.m.wikipedia.org/wiki/Quartzite]
| dredmorbius wrote:
| The McDonald Observatory is open to the public (a consequence, as
| I understand, of it being on the highest-elevation public highway
| (6,814 ft, 2,077m) in Texas, and hence having right of public
| access), with both guided and self-guided tours of several of the
| telescopes / domes, including the 2.7m Smith scope. The damage is
| visible from the public gallery as I recall.
|
| The scope is primarily used for spectroscopic studies, though it
| can also be used for direct visual imaging, which might account
| for why it's even less susceptible to mirror damage than might
| otherwise be the case.
|
| The region is _quite_ rural, with the nearest settlements being
| Fort Davis to the southeast and Fort Stockton to the northeast.
| Among other local attractions are Alpine ( "AL-peen"), home to a
| federal courthouse, and Marfa, a remarkably liberal artist
| colony.
|
| Remarkably beautiful following a freezing frost in winter time,
| as well.
| willguest wrote:
| When all you've got is a hammer, but then remember that you're
| carrying a 9mm...
| dekhn wrote:
| you can always tell a reflector scope person because they'll just
| say "all it did was reduce contrast"
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