[fitswcs] [forwarded] WCS for co-moving maps

[Ian Avruch]

Dear William,

On 09/11/15 21:05, William Thompson wrote:
>> WCSNAME = 'Offset from SSO'
>> NAXIS   =                    3
>>
>> CTYPE3  = 'FREQ    '
>> CUNIT3  = 'GHz     '           / WCS: Unit axis 3
>> SPECSYS = 'SOURCE  '
>> SSYSOBS = 'TOPOCENT'
>>
>> NAXIS3  =                 2001
>> CRPIX3  =               1000.0 / [] WCS: Reference layer index, unit=Scalar
>> CRVAL3  =            1800.0000 / [] WCS: Wavelength, time, ... of reference layer; unit=length,time,...
>> CDELT3  =               5.0E-4 / [] WCS: Scale in 3rd dimension, unit=Length, Duration, ...
>>
>> NAXIS1  =                   11
>> NAXIS2  =                   11
>> CTYPE1  = 'OFLN-GLS'
>> CTYPE2  = 'OFLT-GLS'
>
> Shouldn't this be -SFL instead of -GLS?

Interesting, why do you suggest "-SFL" ?

We follow the AIPS GLS definition (AIPS Memo 46 by E.Greisen), old
as it is. The reference coordinates (alpha_0, dec_0) are the
instantaneous position of the moving target, so by definition equal (0,0).

yours
-Ian


-- 
Ian Avruch  Instrument Scientist / HIFI Calibration
             SRON (www.sron.nl)
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             F (0031|0) 50 363 4033
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