beam order - iraf.net

Welcome to iraf.net Tuesday, May 07 2024 @ 05:43 AM GMT

	Forum Index > Help Desk > General IRAF	New Topic	Post Reply
beam order

Reba

05/06/2008 08:13PM (Read 2014 times)

Newbie

Status: offline

Registered: 03/10/2008
Posts: 5

Hi all,First understand that I am very new to iraf, so i may be asking a very base question, but i have been having a rather simple problem that I am incapable of solving given my limited experience.The problem is that I have been given two fits files. One is the spectra and the other is the associated sigma. What I want to do is combine them so that they are one fits file with the spectra as beam 1 and sigma as beam 2, and both with aperture 1.I am sure that there is most likely a very easy way to do this, but I am afraid that i have been working on it all day with no success. Any help would be greatly appreciated.Thank you,Reba

Profile

Quote

valdes

05/06/2008 08:13PM

Active Member

Status: offline

Registered: 11/11/2005
Posts: 728

Hello Reba,The nomenclature is that an "aperture" is a 1D spectrum with possibly associated data such as the sigma. A "beam" identifies some property of the spectrum such as a object vs sky or an echelle order. A "band" refers to a particular associated spectrum for an aperture. The IRAF spectral formats pack apertures as lines in the first 2D plane. Bands are added as a 3rd dimension in a 3D image.If you just have one spectrum but want to have bands then the image dimension you want is npix x 1 x 2. To create this you can use IMSTACK. The tricky thing here is to get past the fact you want to have only 1 line in the 2D planes of the 3D image.

1:F23B4D71EA Formatted Code

cl&gt; imstack spec1d spec2d     # Make npix spectrum into npix x 1

cl&gt; imstack sigma1d sigma2d  # Make npix sigma into npix x1

cl&gt; imstack spec2d,sigma2d result.ms  # Make multispec format

[/code:1:f23b4d71ea]

This gets the format right.  The last think is to get the header kwywords right.  However for this simple case of a single spectrum you can probably get away with out doing any of this.  The keywords would be

[code:1:f23b4d71ea]

APNUM1  = '1 1 INDEF INDIEF'

BANDID1 = 'spectrum'

BANDID2 = 'sigma'

[/code:1:f23b4d71ea]

In this example the APNUM1 keyword says the first spectrum has aperture number of 1 and beam number of 1 (the first two numbers in the string).

After going through this work you may then realize that other than plotting things with SPLOT that there is little current IRAF spectral software that makes use of the sigma data.

Yours,

Frank Valdes