Just a "barbarous relic"

[vand]

Try telling that to the rocket scientists at NASA:

https://www.nasa.gov/feature/goddard/2016/james-webb-space-telescopes-golden-mirror-unveiled

 

Definitely can't do that with bitcoins.

 

[vand]

oops, this should probably go in the Gold forum! I'm sure a mod will be along shortly..

[Pete]

I reckon you could coat all of these mirrors with less than half a sovereign's worth of gold.

[sovereignsteve]

I hope the Royal Mint haven't been anywhere near it

[vand]

17 hours ago, Pete said:

I reckon you could coat all of these mirrors with less than half a sovereign's worth of gold.

2oz used to coat 6.5msq on the James Webb, apparently - yes, I'm sure it could go even further if needed, we know one of the physical properties of gold it's malleability and ductility.

[SilverTanner]

But would all three different NGC graders give each mirror segment an MS70 cameo?

[Pete]

On 10/10/2017 at 09:38, vand said:

2oz used to coat 6.5msq on the James Webb, apparently - yes, I'm sure it could go even further if needed, we know one of the physical properties of gold it's malleability and ductility.

I would imagine the gold coating is done in vacuum coating machines using sputtering or evaporated thin film techniques.
I haven't researched this but often a mirror coating uses a combination of materials like nickel to help "stick" the atoms together and give better thermal characteristics so the layers don't crack. Because these mirrors are heading to space they might have applied much thicker layers than would be used on Earth to enhance the coating lifetime.

[HawkHybrid]

why did they choose gold and not silver?

silver is more reflective and much cheaper.

this in the reason why I believe the gsr have

been rising. gold is the preferred choice even

if it does cost significantly more.

 

HH

[sovereignsteve]

4 minutes ago, HawkHybrid said:

why did they choose gold and not silver?

silver is more reflective and much cheaper.

probably to do with corrosion resistance

[HawkHybrid]

1 minute ago, sovereignsteve said:

probably to do with corrosion resistance

 

hence silver cannot replace gold?

(milk spots will kill the project  )

 

HH

[Murph]

Silver tarnishes but gold is a better reflector at the red end of the spectrum.  Pity it's terrible at shorter wavelengths at the blue end.  

Aluminium is usually used for  consumer telescopes anyway as it is a better reflector than either silver or gold at something like 520nm and below while still not too far behind silver at longer wavelengths.  Tarnishing and oxidising isn't too much of a problem with aluminium either and it's much cheaper than silver.