In sci.astro.amateur gwatts wrote:
Peter Webb wrote:

...

So its your contention that the atmosphere is transparent all the way up
from microwaves to IR?

I didn't see anything referring to atmospheric transparency in Ms.
Schulter's response but I'll point you to
http://www.alma.nrao.edu/memos/html-...7/memo187.html
or
'MMA Memo 187: Modeling of the Submillimeter Opacity on Chajnantor'

specifically figures 1-6 which show opacities through air paths and
modeled opacities over Mauna Kea, HI. Farther on the authors discuss
predicting opacities over the ALMA site in Chile.

Hi, Peter, and thank you for your correct conclusion that in my post
I really wasn't concerned with transparency or propagation questions,
only with the general question of how to describe what I now have learned
is often called the submillieter portion of the spectrum.


What it comes down to is: No, the atmosphere is not 'transparent all
the way up from microwaves to IR,' but there are windows of transparency
where valuable observations can be made.

That sounds to me like good summary, which would also fit what I recall
from the 1960's about certain regions of EHF -- maybe around 60GHz or
so -- where attentuation or extinction from water vapor is especially
notable. Maybe this is a bit analogous to the absorption lines of
visual spectroscopy.

Of course, as Laura has pointed out, in space this kind of attenuation
is not really a problem!

Something else possibly worth perusing is
http://www.cv.nrao.edu/naasc/present...07_Handout.pdf

and of course the entire ALMA/MMA Memo Series,
http://www.alma.info/

Thanks for these links, which I'll study.

Most appreciatively,

Margo Schulter

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