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I am crosscorrelating spectra with fxcor to determine RV shifts for absorption lines. The spectra are from echelle observations. Each spectrum is the concatenation of all the echelle orders, and is therefore extremely long. (Each spectrum is about 32000 pixels long, corresponding to a wavelength range of 1,500 Angstroms).Once the fxcor task is running, one can display the template spectrum and the object spectrum on a split screen display. For very, very long spectra such as the ones we have, one has to zoom in to see individual lines. This is even more important when scrutinizing filtered vs original objects and templates (we are fourier-filtering our object and template spectra).In pyraf, one cannot zoom in. Is this true or are we overlooking some functionality that would allow us to zoom in on individual spectral features?
In iraf cl (as opposed to pyraf) one can zoom in by using X,Y,Z keys (as is the case in splot). However, even using these zoom-in keys, if the spectrum is tens of thousands of pixels long, once we zoom in, the spectral features appear as if at low resolution. By this I mean that the y-values of the spectrum seem to be discretized. This means that one cannot study the spectral features, a thing that one must do when gauging the fourier filtering parameters.Is there a work-around for this problem, or are we overlooking pre-existing features within the software?Thanks,
Steph

Hi Steph,The X/Y/Z keystrokes are features of the graphics kernel, Pyraf uses it's own graphics and so doesn't implement all of the default keys. Even in the CL this just zooms in on the original graphics buffer and not necessarily the data so you see the discretization of 32K pixel on a screen of a fixed size. Unfortunately, there are no zoom commands built into the FXCOR spectrum mode and I didn't envisage spectra quite that long. For looking at the spectra in this way, have a look at the SPECPLOT task.Cheers,
-Mike