Up: The gainelevation correction of
Following Ruze's (1966) antenna tolerance theory, the normalized
elevationdependent onaxis antenna gain of the reflector optimized at
_{0} is
 
(3) 
where the factor R () takes into account the steepness of
the reflector and the illumination taper of the receiver so that
R is the radioeffective surface deformation
(Greve &
Hooghoudt 1981). The function G(,_{0}) depends
exclusively on the constructionspecific values ()which do not change with time and surface adjustment. The homologycorrected
telescopeindependent flux [S] of a source is obtained from its calibrated
flux [S'()] measured at the elevation by application of
the correction G^{1}(,_{0}) so that^{}
 
(4) 
The literature does not provide explicit information how to deal with
extended sources. We will show that for the specific case of the IRAM 30m
telescope, the onaxis gainelevation dependence
,_{0}) holds also for extended sources not exceeding
in diameter approximately two halfpower beamwidths
(i.e. 2); a weaker gainelevation
dependence applies for more extended sources (i.e. 2 <
). The halfpower beamwidth (FWHP) of the 30m telescope
is = 1.16 [rad], with the wavelength
of observation and D the diameter of the reflector; the relevant beamwidths
are given in Table 1. Note that the diameter of the full beam is
2.4.
Table 1:
Beamwidth of the 30m telescope for receivers
of 13 dB edge taper, and the largest source diameter
^{*} [planet] suitable for determination of the gainelevation
dependence at the specific wavelength

Up: The gainelevation correction of
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