Talk:Speculum metal

There is a grammatical erroe in the first section, which does not have an edit button: "Upon re-polishing the mirror could loose its precise figuring,"

Should use "lose" not "loose" a common error among ignorant internet users.

Please correct it, someone! — Preceding unsigned comment added by 2601:643:4300:1630:AD9E:51B0:B56C:2C54 (talk) 09:13, 6 November 2019 (UTC)

For glass mirrors

"... reflectivity of 68% at 6000 angstroms."

Is this better or worse than the alternatives, or more appropriate for that wavelength, what are the applications? (Expert needed.) Thanks, - 67.174.211.196 (talk) 05:40, 22 January 2010 (UTC)

The use of ångströms has been discontinued in optics. The source is from 1947 and uses Å. Changed it to nanometres now, together with some corrections as per ye olde source.--Micraboy (talk) 09:30, 31 July 2016 (UTC)

Note regarding Newton

I was told by an expert in the history of the English astronomers, that in the times before the invention of the achromatic doublet everyone was talking about "spherical aberration" to describe the shortcomings of refracting telescopes, when in reality it was what we now know as chromatic aberration which was most problematic. My guess is, that Newton thought he needed a parabolic mirror, but when he tried a spherical shape anyways (which is real easy to grind and polish and always a necessary intermediate step before parabolization) he was probaby surprised how well his invention performed. As a mirror does not suffer from chromatic aberration it must have been the first time that someone could see what true spherical aberration really was like. Yes, a high performance newtonian telescope generally does need a parabolic mirror, but in certain designs with a "slow" ratio of focal length to aperture the aberration introduced by a spherical mirror can be negligible, and even in suboptimal designs the resulting performance is still much better than that of a comparable single lens uncorrected for chromatic aberration. --BjKa (talk) 12:37, 4 September 2015 (UTC)

Its not covered here but several sources note Newton was not out to build a reflecting telescope: he wanted to create a proof that the fault in lenses producing color was the uneven refraction in its glass, not its shape. A spherical mirror could supply that proof. Early on description of a lenses problem as "spherical aberration" may point to the notion that if they could just get the right shape, the color would go away.... Newton disproved that. In Newton's time and for 50 years after a single lens telescope could vastly outperform a reflecting telescope of the same diameter, it just had to have a lens with the obscenely long focal length to make the color errors smaller than the focused point they were looking at. They just couldn't do astronomy on windy nights;). Fountains of Bryn Mawr (talk) 14:53, 4 September 2015 (UTC)

Primary source research paper in lead

Per WP:LEAD this does not belong in the lead at all, it does not summarize any important points in the article (in fact its not in the article either). I actually made up a section to put it in the article body, looked up the cited paper to see what few words we should put in the lead to summarize it for the average reader, and found it is unencyclopedic content: it is cited to a primary source with no secondary source interpretation (WP:PST), and it is simply indiscriminate raw data obtained from an experiment of sputtering speculum metal on a sub-strait with no contextual explanations referenced to independent sources that even give the reader a clue as to why they should know this (WP:RAWDATA). Fountains of Bryn Mawr (talk) 01:33, 7 December 2016 (UTC)

Mirror location unknown

The note stating that Hershel's 49.5" mirror is at Science Museum London is no more updated. Here is the reply of the museum :

"Thank you for your enquiry about the first telescope mirror of 49.5" in diameter made by William Herschell. I have searched our collections database and I can confirm this item is not part of our collections". Communication with James Carter, FIO at Science Museum, London, 15 May 2017.

I have also searched for the mirror on other museum, in vain -- lxuroion. — Preceding unsigned comment added by 2001:7E8:C903:400:EDBC:536C:EB8:14C5 (talk) 12:48, 15 May 2017 (UTC)

China? Really?

I keep seeing China listed on every Wikipedia article, yet when I look for the oldest extant archeological find it is NEVER in China, it's almost always Poland or Germany (I suspect Poland because that is where Prussia used to be and they invented a LOT of stuff). I previously noted that China claimed to have invented the brass bell. About 8,000 years before the copper age. Which is pretty astounding. And yet it had so many citations from Chinese academics and western academics alike that somehow, 8,000 years before man first smelted copper, China had brass bells. It's getting kind of tiresome, Wikipedia's reliability is really questionable with the China invented everything first thing.

Do we have any credible reason to believe it besides one author claiming so? Given that we have written documentation, patents, archeological finds, etc from European civilisation, and then some later finds from my current countries region (probably brought here by Europeans), and only THEN do we have Chinese finds showing up. You understand Chinese academics if they want to eat have to retcon history for a living right? Someone will find some poet who wrote a poem about a painting he saw, and interpret that as proof they invented space travel 10,000 years ago.

To make matters worse, we know for a fact that when Chinese nobles traveled the world--because they believed that everything and everyone belonged to their emperor whether they knew it or not--they would 'name' and describe their 'findings' of things. I remember reading of the first Chinese diplomat to travel to ancient Rome. He wrote of the Chinese inventions he found there, such as the coliseum, and the architecture made of marble, and the aquaducts, which he picked Chinese names for, and renamed them all and then spoke of them in their new Chinese names. He truly believed that because the 'world' belonged to the emperor that the Romans were property of him and thus all their inventions were also Chinese inventions. He wasn't like Ibn Fadlan (an early propagandist who traveled the world to regale people back home how barbaric humans are without his religion in their lives) or other traveling diplomats, he legitimately believed what he wrote. All was the emperors. The Roman's were just silly and didn't know they were property of the emperor. And this mentality was not unique, it was and still is intrinsically held in the hearts of many academics back home in China.

It hurts to see westerners unaware of this who take it literally and just believe wholesale everything without looking for any extant archaeological evidence. Anyone can claim they invented something. People lie. Academics lie. Everyone is capable of lying. And when you want to eat, you're willing to write some glorious claims for the party. But you editors here have the opportunity to stop participating in cut and paste journalism / cut and paste academia and ask some hard questions.

I personally think Wikipedia needs a China Did It First policy whereby all claims from China given the spurious history of false claims should be taken with a pinch of salt and further investigation should be explored. That or the claim should be 'Whilst China claims to have invented it, it appears to be a western invention.' as in the case of speculum metal (which we know for a fact was invented in the west, as there are NO chinese mirrors of this nature until around the 1700's).

Sorry for the long winded talk entry, but I just don't think you guys really are aware that you're being taken for a ride with these claims. If we invented literally everything then why did we stop inventing anything after the scientific method / academic means of recording inventions came in? I mean inventing a trillion things a day was a mere banality historically. Yet as soon as being able to prove, patent, and document your invention suddenly zip, zero, zilch, we never invented another thing. Kinda makes you wonder if we invented things, or if we just claimed things for the emperor. 2001:8003:2961:AD00:D872:AD50:B1A7:A343 (talk) 10:30, 18 September 2023 (UTC)