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Old January 2nd 19, 08:35 PM posted to sci.astro.research
Jos Bergervoet[_3_]
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Default Cosmological Problems

On 1/2/2019 8:09 AM, Steve Willner wrote:
In article ,
(Phillip Helbig (undress to reply)) writes:
Visible light is about 0.4 to 0.7 microns (400 to 700 nm (nanometers),


That range is what the human eye can see. In practice, the term
"visible" often refers to light detectable by instrumentation
suitable for visible light, say from 300 nm (the atmospheric cutoff)
to 1000 nm (the intrinsic silicon limit).


(In the same fashion, this silicon is a 'metal' of course!)

...
Typical traditional
ground-based radio astronomy is in the GHz range and below, so
wavelengths from centimetres to metres.


Frequencies up to 15 GHz (wavelength 2 cm) were pretty common even
when I was in school. Nowadays, the VLA
https://public.nrao.edu/telescopes/vla/
makes images up to 50 GHz, and ALMA
https://public.nrao.edu/telescopes/alma/
goes up to 950 GHz (though I don't think the highest frequencies are
100% operational yet).


950 GHz sounds like an interesting LNA design problem!

Is there any pointer to the solutions they use? (Other metals than
silicon, undoubtedly..)

--
Jos