Telluric absorption near H alpha at SPM
9 December 2004
Michael Richer
On 18 November 2004, five spectra of 1800 seconds were
obtained of the white dwarf WD0046+051 for the purpose of studying telluric
absorption near H alpha. The five
spectra were combined and normalized to the continuum level. The result is shown in the following
graph. The dotted line is the
telluric absorption for SPM on the night in question. For comparison, the continuous line shows the telluric
absorption found at Cerro Paranal (R. Napiwotzki, private communication).
The strongest absorption near H alpha has an equivalent
width of only 0.03A. Clearly, only
for emission sources with very narrow lines might one expect an appreciable decrease
in flux. The actual absorption
will depend upon the state of the atmosphere, but was minimal at least on the
night in question.
It is a pleasure to acknowledge the help of Salvador Monrroy
who was the telescope operator for these observations as well as the
participation of Nathan Roche.