About the draft itself Re: WD-SIA-2.0

[Arnold Rots]

But the usage of wavelength in radio astronomy is never precise
and is equivalent to the role band designations (L, C, U, K, ...) play.

I am old enough to remember that some optical astronomers
supported the modernization of replacing wavelength by
wavenumber - physically more meaningful (like frequency).

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Tue, May 6, 2014 at 1:37 PM, Douglas Tody <dtody at nrao.edu> wrote:

> PS-Yes, wavelength in meters - no one's first choice :-)
>>
>
> Wavelength in meters is actually quite a natural unit for radio
> telescopes, which predominantly observe in the centimeter, millimeter,
> and sometimes meter wavelength ranges, although it is true that
> frequency is more commonly used to describe the radio bands.  O/IR and
> UV predominantly use angstroms, microns, and nanometers, all of which
> are wavelength measures.  (But I am sure this will always be a topic
> for heated discussion :-)
>
>
>
>
> On Mon, 5 May 2014, Patrick Dowler wrote:
>
>
>>
>> On 14/04/14 01:00 PM, Arnold Rots wrote:
>>
>>> And what is "barycentric wavelength"? Conversion from frequency to
>>> wavelength as applied at the gravitational potential at the barycenter?
>>> Or does it mean to reduce the spectral coordinate to the barycenter only
>>> dynamically? That's pretty inconvenient for people who are doing
>>> Galactic work.
>>>
>>
>> The intent here is that the BAND parameter only supports one unit (m) and
>> one reference position/time/scale/hard-to-remember thing.
>>
>> Since we have to pick one, can you tell me the one most suitable that
>> would apply to BAND and TIME parameters. Note that the draft currently just
>> refers to the same restricted time metadata as DALI uses for literal values
>> (time scale UTC and unknown reference position). What should we use for
>> wavelength values in the BAND parameter, knowing that implementers will
>> actually just query the wavelength(s) they have in files, filter lookup
>> tables, or spectral wcs already.
>>
>> PS-Yes, wavelength in meters - no one's first choice :-)
>>
>> --
>>
>> Patrick Dowler
>> Canadian Astronomy Data Centre
>> National Research Council Canada
>> 5071 West Saanich Road
>> Victoria, BC V9E 2E7
>>
>> 250-363-0044 (office) 250-363-0045 (fax)
>>
>>
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