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Sensitivity Tables (AO: NGS and LGS)

Notes

  • The sensitivity tables assume photometric conditions (50%-ile cloud cover), grey time (80%-ile sky background) and an airmass of less than 1.2. Note however that the OH sky emission can vary by a factor of ~2 up or down during the night
  • Individual exposure times of 600s were assumed for all cases.
  • Observations are assumed to be at f/32 and dithered (target object in the field at all times); sky subtraction noise is included.
  • The ITC calculates the S/N in an aperture that maximizes S/N given the predicted image quality for the observing conditions and the requested wavelength.


NIRI + ALTAIR (Natural Guide Star, Field Lens)~~~~~~S/N=5 IN ONE HOUR (N.I. OVERHEADS)
Filter Image Quality 
%-ile Bin
Guide Star
R-band (mag)
Guide Star
Distance (arcsec)
Point Source 
Sensitivity (mag)
Strehl Ratio
J 20%-ile 12 0 24.8 0.199
12 5 23.9 0.115
70%-ile 12 5 23.5 0.015
15 5 21.9 0.001
H 20%-ile 12 5 22.9 0.318
70%-ile 12 5 22.4 0.102
15 5 21.7 0.019
K' 20%-ile 12 5 23.2 0.533
70%-ile 12 5 22.7 0.275
 15 22.4 0.126
15 5 22.2 0.040
15 22.1 0.035
85%-ile 12 5 22.0 0.120
H2 1-0 S(1) 70%-ile 12 5 21.8 0.238


NIRI + ALTAIR (Laser Guide Star, Field Lens)~~~~~~S/N=5 IN ONE HOUR (N.I. OVERHEADS)
Filter Image Quality 
%-ile Bin
Point Source 
Sensitivity (mag)
Strehl Ratio
J 20%-ile 24.0 0.111
70%-ile 23.1 0.043
85%-ile 22.2 0.014
H 20%-ile 23.5 0.187
70%-ile 22.8 0.087
85%-ile 22.0 0.036
K' 20%-ile 23.9 0.294
70%-ile 23.3 0.161
85%-ile 22.6 0.081
H2 1-0 S(1 20%-ile 22.1 0.298
70%-ile 21.5 0.164
85%-ile 20.8 0.083