Page 36 - analysis-and-interpretation-of-astronomical-sp

Analysis and Interpretation of Astronomical Spectra 36

Consequences and benefits of the Radiometric Correction with recorded standard stars

The achievable accuracy of this rather delicate method is highly dependent on the quality of
execution. By amateurs it tends to be rather overestimated. Numerous are the potential
sources of errors and in addition, some of the reference profiles of the various databases
show significant differences in their continuum courses.

 Anyway, if applied appropriately and accurately, this fairly time consuming method pro-
vides a reasonable approximation to the original theoretical spectral profile , which

still appears individually reddened by the interstellar matter .

 This way, at least theoretically, also greater fluctuations in the continuum radiation are
detectable.

 The effective temperature according to sect. 18.3 can roughly be estimated.

 This time consuming correction procedure is required if spectra must be obtained for
certain scientific databases. For the intensities of emission lines , even this correction
procedure applies just as a rough approximation (see sect. 8.8).

Correction methods in professional fields

Anyway the professional astronomy applies significantly higher sophisticated and more ac-
curate methods. For most of the large professional telescopes is well known.

is usually determined separately by observations of standard stars with different

zenith distances . This way not a correction curve is generated, but instead a model of the

atmospheric extinction becomes parameterised, like MODTRAN [314]. Thus, finally the pro-
file of the examined object will be corrected in function of the zenith distance [305]. Fur-

ther methods are presented in [300] and [303].

The recording of standard stars consumes valuable telescope time. To relieve the main in-
strument of this "annoying" task, the separate determination of with smaller

“Photometric Monitoring Telescopes” was already proposed [314]. Further possibilities are
based on the measurement of atmospheric Cherenkov radiation as well as on LIDAR [314].

In the infrared range the spectral class A0 shows just few and very faint stellar lines. There-
fore, these more or less purely telluric influenced profiles are generally used to extract the
atmospheric H20 and O2 lines in any stellar spectra [300].