11:ech_blaze--Fit and Apply Ripple Correction

This option consists of two steps as follows:

• 11.1 (ech_fitblz) Model blaze function using a polynomial.

• 11.2 (ech_doblz) Apply blaze function to extracted spectrum.

If flux calibration is not being performed it is sometimes desirable to remove the `blaze' function from the extracted spectrum to assist in fitting line profiles etc. during data analysis.

A task is provided for this purpose which operates by fitting curves to the flat-field orders. The curves can be polynomials, splines or simple fits based on local-median values. The fits may be automatically or interactively clipped and the resulting blaze spectrum is normalised such that its median intensity is unity.

The normalised blaze is then divided into the extracted spectrum. It is important to remember that this operation is performed upon the `extracted' spectrum.

After a blaze function has been applied to the extracted order all its values may be reset to unity to ensure that the order(s) cannot be re-flattened in error (TUNE_BLZRSET=YES). If the blaze is to be re-applied then the correct procedure is to first re-extract the order(s) concerned and then re-fit the blaze.

Parameters:

• BLZFIT - Function for blaze fitting.
• BLZ_INTERACT - YES for interactive blaze-fitting.
• BLZ_NPOLY - Number of coeffs of blaze fitting function.
• FFIELD - Name of flat-field image.
• TUNE_BLZRSET - YES if blaze function to be reset after use.
• TUNE_DIAGNOSE - YES to log activity to debugging file.
• TUNE_MAXPOLY - Maximum coefficients for fits.
• TUNE_NOFLAT - YES if no flat-field frame is available.
• TUNE_YBLAZE - YES for Y-blaze correction.

Reduction File Objects:

• BLAZE_MEDIANS - type: _REAL, access: READ/WRITE.
• BLAZE_SPECT - type: _REAL, access: READ/WRITE.
• DEK_ABOVE - type: _INTEGER, access: READ.
• DEK_BELOW - type: _INTEGER, access: READ.
• EXTRACTED_OBJ - type: _REAL, access: READ/WRITE.
• EXTR_OBJ_VAR - type: _REAL, access: READ/WRITE.
• FITTED_WAVES - type: _DOUBLE, access: READ.
• NO_OF_ORDERS - type: _INTEGER, access: READ.
• NREF_FRAME - type: _INTEGER, access: READ.
• NX_PIXELS - type: _INTEGER, access: READ.
• NY_PIXELS - type: _INTEGER, access: READ.
• TRC_OUT_DEV - type: _REAL, access: READ.
• TRC_POLY - type: _DOUBLE, access: READ.