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Correction for Dust Extinction

To correct observations for total extinction, the contribution from aerosol scattering must be included. Available data (Jones 1984) suggest that to a first approximation the dust scattering at the Roque de los Muchachos observatory does not depend strongly on wavelength over the range considered here. In this case the dust correction term to the extinction curve can be deduced by comparing , the theoretical extinction coefficient in the V band calculated as in (4) above, with the observed mean extinction coefficient in V measured on the night of the observations by the Carlsberg Automatic Meridian Circle group at the Roque de los Muchachos Observatory:

Recent values of for nights of interest can be obtained upon request from the Support Astronomy Group on La Palma (contact Head of Group ext.1316 or E-mail to LPVA::PAC), from the CAMC group at RGO (Cambridge), E-mail CAVAD::LVM or from Starlink in the file:

[LPINFO.EXTINCTION]CAMCEXT.DAT.

The total vertical extinction is then given by:

References

Allen, C.W., 1963 Astrophysical Quantities (London, Athlone Press) 2nd edition. Gast, P.R., 1980 Handbook of Geophysics, U.S.A.F., Cambridge Research Centre(New York, Macmillan). Hayes, D.S. and Latham, D.W., 1975 Ap.J. 197, 593.

Jones, D.H.P., 1984 RGO/La Palma Technical Note No 10.