Resolving power monitoring

October 2004: This section is outdated. We are currently working on an update that will display the results of the Resolving Power monitoring which are being updated in an off-line database. Since the beginning of 2003, all measurements show Resolving Power above 200,000.

The resolving power is measured from the FWHM of the narrowest, reliably measured Th line(s) in the spectrum. Measurements are always done after optimisation of the instrument setup. They do not take into account the intrinsic thermally broadened line width; therefore the values displayed here are lower limits to the true resolving power.

The degradation can be calculated from the thermal broadening v = sqrt(2kT/m) of Thorium lines assuming an operating temperature of the ThAr lamp of 120 C.

Example: at a wavelength of 5400 Å (which is used here as a standard reference wavelength for the CES) the intrinsic width of Thorium lines degrades the measurable resolving power by about 1.0%, 0.35%, and 0.19% for the high-, medium-, and low-resolution image slicers, respectively.

Changes in this nominal resolving power can be due to imperfect instrument alignment (not fully accounted for in the setup) and also to aging of the ThAr lamp, the latter making calculations based on the above formula rather unreliable.

Tabular form:


High-resolution image slicer at standard reference wavelength 5400 Å

Date 1999-03-28 1999-03-30 1999-12-19 2000-01-12 2000-02-12 2000-02-17 2000-10-12 2000-10-14 2000-10-15 2000-10-16 2000-10-21 2001-02-03 2001-02-08 2001-02-09 2001-09-06 2001-09-30 2001-11-10 2001-11-24 2002-01-19 2002-02-08 2002-02-10 2002-08-06 2002-09-14 2003-01-12
High-res. image slicer
Standard reference wavelength 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å 5400 Å
FWHM [px] 2.82 2.51 2.70 2.91 2.99 3.05 2.79 2.62 2.81 2.81 2.72 2.94 3.08 3.00 2.87 2.90 2.99 2.98 2.93 2.99 2.95 2.82 2.82 ----
Resolving power 220000 247000 229000 213000 207000 203000 222000 236000 220000 220000 228000 211000 201000 207000 216000 214000 207000 208000 211000 207000 210000 220000 219000 221000

High-resolution image slicer at other wavelengths

Date 1999-12-20 1999-12-22 1999-12-24 2000-02-13 2000-09-13 2000-09-14 2000-10-12 2000-10-17 2000-10-20 2001-02-03 2001-09-30 2001-12-12 2001-12-17 2001-12-18 2002-01-19 2002-01-19 2002-01-19 2002-01-19 2003-01-12 2003-01-12 2003-01-12 2003-01-12 2003-01-12 2003-01-12 2003-01-12
High-res. image slicer
Other wavelengths: 4554 Å 6170 Å 5896 Å 6781 Å 6300 Å 6300 Å 5790 Å 5896 Å 6247 Å 6138 Å 5782 Å 3864 Å 5882 Å 3974 Å 4028 Å 4028 Å 4028 Å 4028 Å 4050 Å 4229 Å 4385 Å 5951 Å 6150 Å 7722 Å 8790 Å
FWHM [px] 2.77 2.68 2.66 2.86 2.81 2.78 2.70 2.70 2.62 2.75 2.86 2.94 2.94 2.94 2.84 2.63 2.79 2.78 2.65 2.71 ---- ---- ---- ---- ----
Resolving power 227000 237000 220000 215000 219000 222000 226000 218000 228000 235000 212000 217000 199000 209000 215000 232000 219000 219000 223000 229000 227000 224000 227000 218000 220000

Medium-resolution image slicer

Date 1999-12-27 1999-12-29 2000-02-14 2000-10-19 2001-02-03 2002-09-14
Medium-res. image slicer
Wavelength: 3934 Å 5887 Å 8483 Å 3934 Å 6138 Å 5400 Å
FWHM [px] 4.50 4.30 4.55 4.62 4.62 4.72
Resolving power 130000 136000 140000 137000 136000 131000

Low-resolution image slicer

Date 2002-09-14 2002-09-18 2002-09-18
Low-res. image slicer
Wavelength: 5400 Å 6425 Å 6560 Å
FWHM [px] ---- 7.79 6.86
Resolving power 97000 77000 85000

Last update: 04 Oct 2004 Comments to ls-ces@eso.org