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Analysis and Interpretation of Astronomical Spectra 35

8.11 Relative Radiometric Profile Correction by Recorded Standard Stars

Correction methods in amateur fields

With this somewhat time consuming procedure the recorded profile is corrected,

similarly to section 8.10, with a correction function . However is obtained here,

analogously to formula , by a recorded and real existing standard star , mostly of

the spectral type A0V. The continuum course of is very well known and corresponds

to the profile, just reddened by interstellar dust, as it would have been recorded outside the
Earth's atmosphere and without any instrument influences [300]. Such flux-calibrated spec-
tra can eg be found in the ISIS software [410], containing profiles from the MILES-, ELODIE,
UVES and Pickles databases [104], [105], [106], [107].

Standard stars must be recorded with a minimum of time difference and as close as possi-
ble to the object under investigation. Subsequently, the obtained raw profile is divided by
the specific reference spectrum of the very same star from the catalogue. Thus, the atmos-
pheric and instrumental influences can be corrected in a good approxima-

tion. Anyway the resulting spectrum remains here – star-dependent differently strong –
reddened by the interstellar matter , however in the "close range" of a few dozen

light years, just very slightly [209] [11]. In contrast to and the correction function

is determined here only by and , which corresponds also

to common practice in professional astronomy.

In contrast to sect. 8.10 such real standard star correction curves, recorded very promptly
and with similar elevation angle to the investigated object, can be applied to any spectral
classes. With the graphic below, Robin Leadbeater [481] shows, that for different spectral
classes, very similar correction curves are obtained this way (many thanks Robin!).