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IRAF - Image Reduction and Analysis Facility
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What's the output of wtextimage? #400

Closed wuqso closed 4 months ago

wuqso commented 4 months ago

I used wtextimage to convert an IRAF image (1-D spectrum) into a text file and I got 5 columns of numbers as follows,

... 1.713505E-16 2.057833E-16 2.210677E-16 2.126595E-16 1.783040E-16 1.828803E-16 2.377377E-16 2.025416E-16 2.286014E-16 1.988441E-16 1.746359E-16 2.029601E-16 1.971067E-16 1.760395E-16 1.854584E-16 1.573641E-16 1.902356E-16 2.273310E-16 1.731561E-16 1.787992E-16 1.891723E-16 1.735168E-16 1.931826E-16 1.961806E-16 1.954478E-16 2.234496E-16 1.922625E-16 1.898011E-16 2.206757E-16 2.060543E-16 ...

What are these numbers? If I don't make a mistake, the wtextimage should produce a text file with columns as wavelength, flux, and flux error, ...

olebole commented 4 months ago

The numbers are just the pixel values of your file, as documented in the help file of wtextimage:

IRAF images are converted to text files with procedure wtextimage. The text file written consists of an optional header optionally followed by the pixel values. The pixels are output in FITS order, that is, the leftmost subscript varies most rapidly. The image header is written in the "keyword = value / comment" format of FITS.