Scrunching

The .iar file can be used by the FIGARO iscrunch program in order to correct and calibrate your data files:

 % iscrunch object2d

You will then be asked for the name of the .iar file:

FILE - (FIle) File containing results of 2D arc fit /''/ >

enter arcframe2d.

The next question asks how many bins (pixels) you would like your new image to have. The simplest answer is to keep the same number of pixels that you had in your original image, hence for this file enter 1024

The next question ask if you want to sample your data in logarithmic bins, enter false.

You will now be asked for the start and end wavelengths of your data, use the numbers noted earlier after the dispersion had been calculated.

WSTART - (WStart) Wavelength of center of first bin /6693.583/ > 6705.248
WEND - (WEnd) Wavelength of center of last bin (or increment) /6759.628/ > 6754.836

The next question asks if the data should be treated as a flux per unit wavelength. Typically for data from spectrometers the answer to this is false.

Reply true to use quadratic interpolation for the data at the next question.

The final question asks for the output filename, e.g. object2dscrunch:

OUTPUT - (OUtput) Name of resulting scrunched image /''/ > object2dscrunch

We can now view this scrunched file using:

   % display object2dscrunch clear mode=pe accept

which should look something like the figure below.

Figure: The data frame, now calibrated and curvature corrected.

A further check on the process is to scrunch the arc frame, in order to check that the arc lines do indeed come out perfectly straight.