OAC - Astronomical Observatory of Capannori

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Comune di Capannori

MEASURING ATMOSPHERIC EXTINCTION

In order to compute correct magnitudes by means of photoelectric photometers, we need to estimate the atmospheric extinction coefficients at the various photometric bands we use. There are some different methods (for example read 'Astronomical Photometry' by Henden & Kaitchuck, or 'Photoelectric photometry of variable stars' by Hall & Genet) to estimate the atmospheric extinction coefficients; the best of them is the method of Bouguer's lines. This is the one we regularly use.
At OAC we have done this hundreds of times; below you can see the graphs of the Bouguer's lines for UBVR bands in the same night.

DETERMINING EXTINCTION COEFFICIENTS

K'V measured at OAC with the 60 cm Cassegrain by means of the method of Bouguer's line on October 3rd 2014. Star: M45 F (rising).

K'B measured at OAC with the 60 cm Cassegrain by means of the method of Bouguer's line on October 3rd 2014. Star: M45 F (rising).

K'U measured at OAC with the 60 cm Cassegrain by means of the method of Bouguer's line on October 3rd 2014. Star: M45 F (rising).

K'R measured at OAC with the 60 cm Cassegrain by means of the method of Bouguer's line on October 3rd 2014. Star: M45 F (rising).

Below there are some plots of Bouguer lines obtained with the 30 cm Schmidt-Cassegrain telescope of OAC.

We regularly monitor the extinction coefficients and we compare them with LIDAR information about atmospheric dust; the two time series correlate well. So we make an environmental use of atmospheric extinction measurements.

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