About the draft itself Re: WD-SIA-2.0

[François Bonnarel]

Le 06/05/2014 19:37, Douglas Tody a écrit :
>> 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 :-)

and Xray observers use Kev , Mev gamma ray use GeV and Tev. That's 
pretty small in meters.
I encountered the problem once in discussing with Hess/CTA group

Regards
François
>
>
>
> 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)
>>