ECHIMDIVIDE

Purpose:

Script to divide a series of extracted échelle spectra by an extracted flat-field and then rescale to the original means of the spectra.

Language:

IRAF cl script.

Description:

This script is for removing the blaze function of an extracted échelle spectrum. In this particular case an extracted flat-field spectrum is used to divide-out the blaze function. The script proceeds by dividing the échelle image by the flat field. This will lead to some change in the mean flux level in the orders of the spectrum. To remove the level shift, the mean value of each order in the input image and in the flat-field-divided image is found. A `correction' ratio for each order can then be calculated and used to rescale the output image so that the resulting blaze-corrected image retains the same per-order mean level as the input. By calculating a per-order mean, rather than rescaling the image by a single factor, the order-to-order blaze corrections are retained.

Usage:

The flat parameter is the name of an extracted flat field.

The input and output lists of spectra may be the same.

To install and use:

1. Place script in your IRAF home$ directory as echimdivide.cl.

2. Interactively type:

      cl> task echimdivide=home$echimdivide.cl
   

3. Or, in your login.cl or loginuser.cl place the following before the keep:

      task echimdivide = home$echimdivide.cl
   

4. Run the task by typing:

      cl> echimdivide
   

   You will be prompted to enter values for the parameters. Alternatively, set values using the parameter editor and then run the task.

Source code:

The script source code is available here.