'n Hulpteleskoop van die Europese Suidelike Sterrewag wat die gunstige waarnemingstoestande van die Atacamawoestyn benut
Afrikaans: In die hart van die Atacamawoestyn, tuiste van die Paranal-sterrewag, sak die son met die aanbreek van nog 'n glashelder nag. Hierdie aanskoulike foto, geneem deur die ESO-foto-ambassadeur Gianluca Lombardi, toon een van vier hulpteleskope (HT's) wat deel uitmaak van die Europese Suidelike Sterrewag (ESO) se Baie Groot Teleskoop (BGT). Dit pryk hier teen 'n rosig-blou aandlug met 'n volmaan wat met 'n rooi skynsel bo die horison hewe. Hierdie kleur is naamlik die gevolg van ligverstrooiing in die atmosfeer. Wanneer die maan nouliks bo die horison hang, volg die maanlig 'n langer trajek deur die atmosfeer, en die effekte van verstrooiing word derhalwe verhoog. Aangesien rooi lig minder verstrooi word as lig van korter golflengtes soos groen of blou, neem ons dan 'n rooier maan waar. Hierdie effek is terloops minder treffend op plekke soos Paranal, waar die skoon lug minder stof en onsuiwerhede bevat wat verstrooiing bevorder. Benewens hierdie skoon lug sorg Paranal se afgesonderde ligging, ver van die beskawing en gepaardgaande ligbesoedeling, vir ideale omstandighede vir landgevestigde sterrekunde. Die 1,8-meter hulpteleskope vorm ook 'n integrale deel van die BGT-interferometer (BGTI). Wanneer die eenheidteleskope meermale vir onafhanklike aktiwiteite aangewend word, bly die observasierooster van die HT's volkome aan die interferometer toegedeel. 'n Voordeel hiervan is dat die HT's deurlopende onafgebroke moniterings kan uitvoer wat uitsonderlik akkurate vasstellings van objekposisies oplewer. Dit staan ​​bekend as die smalhoek-astrometrie-modus van die BGTI. Die hulpteleskope is mobiel en kan tussen 30 verskillende waarnemingsposisies verskuif word. Deur die hele Paranal-platform sodanig aan te wend, is 'n skeiding van 202 meter tussen HT's moontlik – die langste basislyn van die BGTI. English: Deep in the heart of the Atacama Desert, home of the Paranal Observatory, the Sun is setting at the start of another clear night. This charming photograph, taken by ESO Photo Ambassador Gianluca Lombardi shows one of four Auxiliary Telescopes (ATs) that belong to ESO’s Very Large Telescope (VLT) sitting boldly against a vivid sky of pink and blue. The full Moon, seen hovering over the horizon, has a distinctly reddish hue, a phenomenon caused by the scattering of light by Earth’s atmosphere. When the Moon is close to the horizon, the light we see from it must travel through a greater thickness of the atmosphere, so the effects of scattering are increased. As red light is more resilient to scattering than green or blue, our view of the Moon is reddened. As it happens, the reddening effect is somewhat less pronounced at sites like Paranal, as the clear air contains fewer particles that cause scattering. In addition to this, Paranal’s isolated location, far from civilisation and hence sources of light pollution, makes it a perfect place for ground-based astronomy. The 1.8-metre Auxiliary Telescopes are integral to the VLT Interferometer (VLTI). Whereas the Unit Telescopes are very often engaged in independent activities, the ATs devote all their time to the interferometer. One advantage of this is that the ATs can be used for regular, long-term monitoring observations, which allow exceptionally precise measurements to be made of object positions; this is known as the Narrow Angle Astrometry mode of the VLTI. The ATs telescopes are mobile and able to relocate between 30 different observing positions. By utilising the entire Paranal platform this way, a separation of 202 metres between ATs is possible — the longest baseline of the VLTI.