2.7-meters Telescope mirror shot 7 times (1970)
cbat.eps.harvard.edu
cbat.eps.harvard.edu
Wait, did they say scratches? They meant a completely cracked front element.
https://www.lensrentals.com/blog/2008/10/front-element-scrat...
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.
Thus a link to the process would be useful - even if searching for reviews of that process would show it does not work.
I’m sure there are more authoritative links but i picked this one because i thought it said ‘burningeye.com’ at first:
In the UK my doctors and NHS notes say there is no evidence that this works.
The removal of the vitreous humour does work but the doctors at Moorfields, the top UK eye hospital, do not recommend it as it has what they say is a high risk of making things worse. They will do it but you have to be really really certain that the floaters are impossible to live with.
I’m not sure ‘breaking up’ floaters would even be desirable, they are still going to be in there making visual noise.
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.
As for asking for the name it is that which helps to see that we talk about the same thing without that it is impossible to know what you are talking about.
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.
There's an amusing picture where a large owl has blocked a substantial portion of the view:
This is useful, however, for focussing using a bahtinov mask.
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.
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.
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...
> 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.
> People who know better: Depressed employee did some minor damage
Modern LEO techniques seem to have history.
"The damage is limited to small craters about 3 to 5cm in radius, which reduce the light collecting efficiency by about 1 percent"
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
(this is true)
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)
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.
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.
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.
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.
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
>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.
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.
If you would like to see the bullet holes. Bigger than I imagined based on the telegram.
They definitely told us the story and all the kids were like “coool!”
"no sir, that bigger hole was there before the incident... yes sir, it is supposed to be there"
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.
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.
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.
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.
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.
And all right in the world.