A Lunar Observatory

From time to time astronomers put forward proposals for observatories on the surface of the Moon. There are sound technical reasons for placing instruments outside of the Earth's influence but, to the general public, which sees only the 'gee whiz' portions of astronomical research (e.g. Hubble Space Telescope (HST) images) through mainstream media, there may seem to be little justification. So, why are Moon-based observatories desirable, and what are the pros and cons?
A Lunar Observatory Essay PDF

Calculating a Free-Free Absorption Model for PKS 1718-649

This paper discusses free-free absorption as the driver of spectral shape in gigahertz peaked spectrum (GPS) sources. Two models (Tingay and Murphy 2001; Bicknell et al. 1997) are applied to high-precision spectral data for the PKS 1718-649 GPS source gathered using the Australia Telescope Compact Array (ATCA) (Tingay and de Kool 2002). The suitability of each model is assessed against the ATCA data. The Bicknell et al. model provides an excellent fit and is tested against third party data at higher and lower frequencies to test its validity outside the range of the ATCA data. Outside the ATCA range the model is less accurate, and reasons are discussed.
Calculating a Free-Free Absorption Model for PKS 1718-649