extracting 1D spectra
rbarrows wrote on Jul 11, 2008
Hi,
I am wondering if there is a simple way to just create a 1-D (flux vs wavelength) spectra from a 2-D longslit spectral image by just specifying a position along the slit.
For example, I have a 2-D spectral image in fits format (from STIS): o5cr010c0_x2d.fits. This seems like a simple thing to do I am just not familiar enough with IRAF and related packages to know what task(s) to use. If anyone can let me know of a simple way to do this I would greatly appreciate it. Thanks so much.
I am wondering if there is a simple way to just create a 1-D (flux vs wavelength) spectra from a 2-D longslit spectral image by just specifying a position along the slit.
For example, I have a 2-D spectral image in fits format (from STIS): o5cr010c0_x2d.fits. This seems like a simple thing to do I am just not familiar enough with IRAF and related packages to know what task(s) to use. If anyone can let me know of a simple way to do this I would greatly appreciate it. Thanks so much.
Francisco Valdes wrote on Jul 11, 2008
Hello,
The usual way to extract 1D spectra from 2D data is with the twodspec.apextract package. Admittedly this is a fairly sophisticated package with lots to learn for the novice. But it may be good for you to learn about it and look over the documents of spectral reductions in the docs area of the iraf.net site.
The simplest way to do a simple column or line sum of a 2D spectrum is with the task SCOPY in the ONEDSPEC package.
In the ONEDSPEC package tasks which work on 1D spectra automatically convert 2D spectra using dispaxis, nsum, and aperture. The "aperture" parameter is the row or column in the 2D spectrum which is the center of the spectrum you want to extract. Note that instead of using SCOPY you could use SPLOT to do the conversion internally and get a graph of the spectrum.
Yours,
Frank Valdes
The usual way to extract 1D spectra from 2D data is with the twodspec.apextract package. Admittedly this is a fairly sophisticated package with lots to learn for the novice. But it may be good for you to learn about it and look over the documents of spectral reductions in the docs area of the iraf.net site.
The simplest way to do a simple column or line sum of a 2D spectrum is with the task SCOPY in the ONEDSPEC package.
cl> onedspec
cl> onedspec.dispaxis=2 # 1=spectrum along rows, 2=spectrum along cols
cl> onedspec.nsum=10 # Number of rows/columns to sum
cl> scopy spec2d spec1d aper=50
In the ONEDSPEC package tasks which work on 1D spectra automatically convert 2D spectra using dispaxis, nsum, and aperture. The "aperture" parameter is the row or column in the 2D spectrum which is the center of the spectrum you want to extract. Note that instead of using SCOPY you could use SPLOT to do the conversion internally and get a graph of the spectrum.
Yours,
Frank Valdes
Last post on Jul 11, 2008