Estimating the EIS spatial resolution using observed features#

If an observed solar feature has a size much smaller than 1 arcsec and is also much brighter than the surrounding plasma then it will be seen by EIS as a point source, and thus will reveal the point spread function of the instrument. Such brightenings are quite common at transition region temperatures in active regions.

This method was used by Young (2004) for estimating the PSF of SOHO/CDS.

This page lists examples of small, intense brightenings, with links given to figures showing the variation of line intensity along the EIS slit. The spatial resolution can be considered to be the full width at half maximum of the brightening.

12-Dec-2006, 19:07 O V 192

20-Jan-2007, 22:32 O V 192, Mg V 276

The examples above suggest to me that the spatial resolution is about 3-4 arcsec in the Solar-Y direction.

Caveats#

• This method leads to an upper limit to the spatial resolution. If other brightenings are found with narrower widths, then users are encouraged to post details here.

• The spatial resolution will vary along the EIS slit, so the location of the brightening on the detector is important.

Peter Young, 25-Mar-2008