Mount Pinatubo and Atmospheric Extinction at Mount John University Observatory 1987-94

Aims: The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with an accuracy of 0.01 mag/airmass. Methods: The extinction curve of Paranal was obtained through low-resolution spectroscopy of 8 spectrophotometric standard stars observed with FORS1 mounted at the 8.2 m Very Large Telescope, covering a spectral range 3300-8000 A. A total of 600 spectra were collected on more than 40 nights distri...

We determine the volcano climate sensitivity and response time for the Mount Pinatubo eruption. This is achieved using observational measurements of the temperature anomalies of the lower troposphere and the aerosol optical density (AOD) in combination with a radiative forcing proxy for AOD. Using standard linear response theory we find sensitivity = 0.18 +- 0.04 K/(W/m2), which implies a negative feedback of -1.0 +- 0.4. The intrinsic response time is 5.8+-1.0 months. Both r...

Sky conditions in the remote, dry north-western interior of South Africa are now the subject of considerable interest in view of the imminent construction of numerous solar power plants in this area. Furthermore, the part of this region in which the core of the SKA is to be located (which includes SALT) has been declared an Astronomical Advantage Zone, for which sky brightness monitoring will now be mandatory. In this project we seek to characterise the sky brightness profile...

We present a new atmospheric extinction curve for Mauna Kea spanning 3200--9700 \AA. It is the most comprehensive to date, being based on some 4285 standard star spectra obtained on 478 nights spread over a period of 7 years obtained by the Nearby SuperNova Factory using the SuperNova Integral Field Spectrograph. This mean curve and its dispersion can be used as an aid in calibrating spectroscopic or imaging data from Mauna Kea, and in estimating the calibration uncertainty a...

The Hunga Tonga-Hunga Ha'apai volcano erupted on 15 January 2022 with an energy equivalent to around 61 megatons of TNT. The explosion was bigger than any other volcanic eruption so far in the 21st century. Huge quantities of particles, including dust and water vapour, were released into the atmosphere. We present the results of a preliminary study of the effects of the explosion on observations taken at Paranal Observatory using a range of instruments. These effects were not...

The Observatorio del Roque de los Muchachos (ORM), in the Canary Islands (Spain), was one of the candidates to host the future European Extremely Large Telescope (E-ELT) and is the site of the Gran Telescopio Canarias (GTC), the largest optical infrared facility to date. Sky transparency is a key parameter as it defines the quality of the photometry to be acquired in the astronomical observations. We present a study of the atmosphere extinction at the ORM, carried out after a...

The study of atmospheric extinction based on the MASS data has been carried out using the classical photometric pairs method. The extinction in V band can be estimated at 0.m 19. The water vapour content has been derived from GPS measurements. The median value of PWV for clear nights is equal to 7.7 mm.

In order to maximize the scientific return of the telescopes located at the Paranal Observatory, we analyse the properties of the atmosphere above Paranal in the near-infrared (NIR). We estimate atmospheric extinction in the spectral range 1.10-2.30 um (J, Js, H, and Ks) using standard stars that were observed during photometric and clear nights with ISAAC on the Very Large Telescope UT1 between 2000 and 2004. We have built a database consisting of hundreds of observations, w...

Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. $C_n^2(h)$ profiling indicates a weak layer located at 12 - 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 - 8 km above sea level. $V(h)$ profiling suggests that tropopause layer velocities are nominally 12 - 30 m/s, and near...

Over 30 years of solar data have been acquired by the Birmingham Solar Oscillations Network (BiSON), an international network of telescopes used to study oscillations of the Sun. Five of the six BiSON telescopes are located at major observatories. The observational sites are, in order of increasing longitude: Mount Wilson (Hale) Observatory (MWO), California, USA; Las Campanas Observatory (LCO), Chile; Observatorio del Teide, Iza\~{n}a, Tenerife, Canary Islands; the South Afr...