Changes between Initial Version and Version 1 of SpectralRange


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Timestamp:
06/09/05 12:26:04 (16 years ago)
Author:
joe
Comment:

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  • SpectralRange

    v1 v1  
     1== Spectral Range == 
     2 
     3The electromagnetic wavelength interval or equivalent over which 
     4observations are made is the fundamental discriminator among many 
     5types of solar image and other data.  The model needs to apply to both 
     6narrow-band ("monochromatic" or single-line) and broad-band data. 
     7Different branches of the field use different units depending on their 
     8spectral band -- frequency at the lowest ranges (of frequency), wavelength 
     9at intermediate ranges, energy at the highest.  Again for the sake of 
     10simplicity we define a single model, assuming that the necessary 
     11conversions can be simply made. 
     12 
     13 
     14 
     15==== Wave_Type ==== 
     16 
     17 
     18  type: ''menu''[[BR]] 
     19  FITS keyword: ''WV_TYPE''[[BR]] 
     20 
     21  The class of spectral data, relating to both the nominal spectral 
     22bandpass and the spectral target.  Three values are recognized: 
     23 
     24  ''' broad ''' 
     25 
     26 
     27    Indicates that the spectral range of the measurement is large 
     28compared to the width of absorption/emission lines within the range, 
     29and encompasses multiple lines as well as continuum (unless blanketed) 
     30 
     31  ''' line ''' 
     32 
     33 
     34    The spectral range of the measurement is of the same order or less 
     35than the width of the target line, and is centered on a wavelength within 
     36the wings of the line. 
     37 
     38  ''' narrow ''' 
     39 
     40 
     41    The spectral range of the measurement is of the same order or less 
     42than the typical width of lines in the neighborhood, but is centered on 
     43a continuum wavelength, outside of any significant lines.  This designation 
     44is used to distinguish narrow-band continuum (or "white-light") data from 
     45true broad-band data.  For data of this description, the matching spectral 
     46range should be much broader than the instrumental bandpass, on the 
     47understanding that the data are proxies for broadband measurements. 
     48 
     49The exact definition of the bandpass (''e.g.'' FWHM) is not prescribed, 
     50but is left up to the terminology of the data provider.  In the absence of 
     51a provider definition, FWHM should be used. 
     52 
     53 
     54==== Wave_Minimum ==== 
     55 
     56 
     57  type: ''number''[[BR]] 
     58  unit: ''Ångström (10nm)''[[BR]] 
     59  FITS keyword: ''WV_MIN'' 
     60 
     61==== Wave_Maximum ==== 
     62 
     63 
     64  type: ''number''[[BR]] 
     65  unit: ''Ångström (10nm)''[[BR]] 
     66  FITS keyword: ''WV_MAX'' 
     67 
     68  The nominal minimum (maximum) of the observing spectral bandpass 
     69associated with the data.  As discussed above, for narrowband continuum 
     70data, the range should be much larger than the instrumental bandpass; 
     71it should correspond to the spectral range over which the data are 
     72useful as a proxy, typically an octave or more. 
     73 
     74 
     75==== Wave_Bands ==== 
     76 
     77 
     78  type: ''number''[[BR]] 
     79  FITS keyword: ''WV_NBAND''[[BR]] 
     80 
     81  The number of wavelength bands in the observation 
     82 
     83 
     84==== Wave_Step ==== 
     85 
     86 
     87  type: ''number''[[BR]] 
     88  unit: ''Ångström (10nm) / pixel''[[BR]] 
     89  FITS keyword: ''WV_STP''[[BR]] 
     90 
     91  The spectral dispersion