The telescope efficiencies (main beam and aperture efficiency) are given in Appendix A of ``The 30m Manual'' and the IRAM newsletter No. 18, (November 1994). A one-page summary of the telescope system is on the web (http://www.iram.es/Telescope/systsumm.ps).
At 1.3 mm (and a fortiori at shorter wavelengths) a large fraction of the power pattern is distributed in an error beam which can be approximated by two Gaussians of FWHP and 800'' (see [16, 1] for details). Astronomers should take into account this error beam when converting antenna temperatures into brightness temperatures. The effect is particularly important at 0.8 mm, where the power in the first error beam of FWHP is twice larger than in the main beam.
The aperture efficiency depends somewhat on the elevation, particularly at shorter wavelengths. This gain/elevation effect is evaluated in .