LWS
Quick Reference
This page summarizes the imaging capabilities of the LWS. The values are emperical determined using images acquired during engineering and science observing sessions.  

Estimated Imaging Performance

scale at detector 0.0011 arcsec/µm;
Detector pixel scale 0.0847 arcsec/px (75 µm/px) 
Field of view 10.84×10.84 arcsec
Flexture <0.2 arcsec (<3 px) during 3 hour transit near zenith
Expected count rate 11,000 ADU/Jy·sec at 11.7 µm filter from sky
Mode changes 2 min changeover between imaging and spectroscopy

Filter wavelength1
µm		 FWHM2;
arcsec		 Sensitivity 3
mJy/sec 		Zeropoint 
L 3.9 Seeing Limitted 520 23.67
M 4.7 Seeing Limitted N/A N/A
8.0 8.37 0.17 N/A N/A
8.9 8.88 0.18 N/A N/A
9.9 9.89 0.20 N/A N/A
10.7 10.67 0.22 N/A N/A
11.7 11.69 0.24 N/A N/A
SiC 11.81 0.24 15.0 22.66
12.5 12.62 0.26 N/A N/A
17.65 17.73 0.36 110 19.25
18.75 18.75 0.39 N/A N/A
23.1 23.10 0.48 N/A N/A
24.5 24.53 0.51 N/A N/A

Transmission curves for the filters available in the LWS may be found on the filter page.

A Time Estimator is available on the LWS web site that predicts the amount of on-source integration time is needed to acquire a user specified signal-to-noise.

Notes:

  1. Average wavelength between the half-power points of the transmission curve. The average wavelength does not always agree with the wavelength for the name of the filter.
  2. Assumes diffraction limitted imaging with a 10 m diameter primary mirror.
  3. Signal level yielding S/N=1 in 1 sec (on source time) at stated wavelength over the filter bandwidth, integrated over the detector area extending from the point source center to the first null in the Airy pattern. Elapsed time is typically 3 times longer than the on-source time due to chop-nod inefficiencies.
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Last modified: 8 Apr  2002