What is the instrumental width of 2" EIS slit ? The I.W. of 1" slit is approximately 0.055 A, however, there is big confusion with 2". This must be higher, however, in what values? What should be its value range ?--- A.K. Srivastava

The instrumental width of the 2" slit has not yet been determined but Charlie Brown (NRL) is working on this. We will update the wiki when the value is known.

--LouisaBradley, 12-Sep-2007

I've taken two quiet Sun rasters taken a day apart, one obtained with the 1" slit and the other obtained with the 2" slit. Plotting histograms of the FWHM of the 195.12 emission line gives the result shown in the figure below.

Note that I've subtracted out a thermal width for Fe XII 195.12 of 21 milli-angstroms. Taking the weighted average of the histogram distributions gives 65.0 mAng for the 1" slit and 72.0 mAng for the 2" slit. I thus estimate that the instrumental width for the 2" slit is 7 mAng larger than that for the 1" slit.

The data-sets I used were 2008 January 21 16:02 (SYNOP002, 1") and 2008 January 22 16:00 (cam_qs_2as_context, 2"). Both were obtained close to Sun centre. The two rasters have different sizes which may account for the different shapes of the width distributions.

A study has been designed to obtain a 2" raster directly after a 1" raster for the purposes of comparing the instrumental widths of the two slits, and so the above result should be considered as preliminary until data from the new study are available.

--Peter Young, 2-Apr-2009