Multiplying by a 1D BBody spectrum

jsb3r wrote on Jul 20, 2009

Help. I am attempting to multiply a telluric corrected spectrum by an artificial blackbody spectrum I created with MK1DSPEC. The corrected spectrum looks fine and so does the blackbody spectrum. However, when I use SARITH to multiply the two, I get nothing but the zero error values. I have used disptrans to change the units on the wavelength values for the BBody from angstroms to microns. I've use WSPECTEXT to make text files with the actual wavelength and flux values for each of the spectra. They look fine with the exception of a string of zero values. However, I wouldn't expect this to cause SARITH to spit out a completely useless output. I'm pretty sure that I am choosing the correct apertures for each FITS file since the target spectrum is in [1] and the BBody is saved in [0]. I've added WSTART and WEND to the header of the BBody fits file. Although, I don't think that SARITH really cares. I still get nothing but zeros. What am I missing?

Thanks,

Jeff

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Francisco Valdes wrote on Jul 20, 2009

I can't tell what might be wrong. The main thought is that SARITH matches data by wavelength and any points which lie outside the other are given a value of zero. Therefore if the task things the spectra don't overlap you will get a spectrum of zero values. It sound like you have tried to check that the wavelengths are right. The test I would do is use SPECPLOT to plot the two spectra stacked on each other. You could also use SPLOT with the "overplot" key and then reading the second spectrum, but this might still be unclear.

If you still can't figure this out you can send long header listings of the two spectra ("imhead <spectra> l+") and the output of "imstat <spectra>".

Note that if you think you have the spectra sampled identically so they match in pixel space then you could also just use imarith to multiple the spectra as simple image vectors.

Yours,
Frank Valdes

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Last post on Jul 20, 2009