This page is a copy of one on the JACH/UKIRT Web page.

     Mauna Kea summit extinction values (Dec 1980 through May 1996)
 
Given below are the mean extinction values, the mean error of the mean,
the median values, and the number of measurements.  When in doubt, use
the median values.
 
For more information see Krisciunas et al., PASP 99, 887, 1987.
 
Data for broad band filters:
 
Wavel/Filter       mean            median         n
               (mag/air mass)   (mag/air mass)
 
(0.36) U      0.358                 0.358         1

(0.44) B      0.198 +/- 0.008       0.194        45
 
(0.55) V      0.119     0.005       0.111        52
 
(1.25) J      0.114     0.007       0.102       111
 
(1.65) H      0.068     0.006       0.059       110
   
(2.2)  K      0.096     0.005       0.088       156
 
(3.4)  L      0.203     0.030       0.150        31
 
(3.8)  L'     0.112     0.009       0.093        96
 
(4.8)  M      0.244     0.016       0.220        60
 
(10)   N      0.184     0.017       0.151        50
 
(20)   Q      0.503     0.030       0.451        43
 
(32)   Z      1.398     0.313       1.14          6
 
Data for narrow band filters:

    nbM     0.194 +/- 0.025       0.193        11  *
 
    7.8     0.413     0.040       0.458        17
 
    8.7     0.144     0.020       0.135        27
 
    9.6     0.185     0.026       0.189        17
 
   10.3     0.107     0.026       0.092        20
 
   11.6     0.101     0.026       0.088        20
 
   12.5     0.149     0.038       0.125        22
______________
 
    * Narrow-band M filter at UKIRT in UKT9, range 4.59 to 4.75 microns.

From the CFHT Bulletin, number 19, p. 16 (1988) we obtain the
following mean optical/near-IR extinction values:

   wavelength (A)      mag/airmass

      3000                4.90
      3100                1.37
      3200                0.82
      3300                0.57
      3400                0.51

      3500                0.42
      3600                0.37
      3700                0.33
      3800                0.30
      3900                0.27

      4000                0.25
      4250                0.21
      4500                0.17
      4750                0.14
      5000                0.13

      5250                0.12
      5500                0.12
      5750                0.12
      6000                0.11
      6500                0.11

      7000                0.10
      8000                0.07
      9000                0.05
     10000                0.04
     12000                0.03

Frankly, the 1.2 micron extinction value here seems much too low.
And I would think that at 1.0 microns we are looking at the edge 
of the J-band, which is affected by water vapor absorption.  


A graph from the CFHT observer's manual may be obtained by clicking
here. 


One might also calculate the expected extinction from the
treatment laid out by Hayes and Latham (1975),  Astrophysical
Journal ,  197 , 593, with the appropriate
height inserted.  Hayes and Latham give 1.5 km as the aerosol
scale height.  I found it to be 1.43 +/- 0.43 km from actual 
measurements at Mauna Kea.  (See Krisciunas, 1990,  Publ. 
Astr. Soc. Pacific ,  102 , pp. 1052-1063,
on p. 1054.)