Estimation of the slit function to check the stability
To monitor the stability of the slit function, a slit function is estimated in one order in both spectral channel. The orders are used where the Ca H+K and H alpha lines, respectively, are located. To estimate the slit function, the bias and the background are removed form the image. After this, the corresponding order is extracted with the defined extraction width and
normalised:
| |
im(i,*) = im(i,*)/∑(im(i,*)),
|
where i is the column in the extracted order.
Finally, the slit function is estimated as the median of the counts in dispersion direction and the equation is:
where j is the row in the extracted order.
To monitor the slit function, the relative centre and the FWHM of the slit function are calculated with a
Gaussian fit and plotted this vs. the UT time.
For this plot only data with a Signal to noise ≥ 25 are used.