Interest in astronomy Isaac Roberts

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starfield: isaac roberts s observatory , home in crowborough, sussex


in 1878, roberts had 7-inch refractor @ home in rock ferry, birkenhead. although @ time used visual observation, began explore stellar photography, forte, few years later. in 1883, roberts began experimenting astrophotography. first used portrait lenses apertures varying









3
8








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8 inches. roberts pleased results, , ordered reflecting telescope silver-on-glass mirror of 20-inch diameter (100-inch focal length) howard grubb , 1885 had built observatory building house it. mounted photographic plates directly @ prime focus avoid loss of light occur using second mirror. allowed him make significant progress in then-developing field of astrophotography.


in 1886 roberts displayed first photographs @ royal astronomical society @ liverpool, president. these images showed, first time, vast extensions of nebulosity in pleiades , orion.



advancements

isaac roberts magnum opus considered picture of great nebula in andromeda


astrophotography requires long exposure times (sometimes hour or more) record faint objects on photographic plate. long exposure record objects invisible human eye. isaac roberts developed technique of piggyback astronomical photography, mounting camera/lens on larger equatorial mounted telescope used guidescope . combination kept camera aimed accurately on long exposure time earth rotated.


most consider roberts magnum opus photograph showing structure of m31, great nebula in andromeda (now known andromeda galaxy) taken on 29 december 1888. long exposure photograph revealed nebula had spiral structure, quite unexpected @ time. photographs such changed astronomy revealing true form of nebulae , clusters, , helped develop theories galaxies. published celestial portfolio in large format book first popular account of celestial photography of deep sky.


in addition considerable advancements in field of astro-photography, roberts invented machine called stellar pantograver engrave stellar positions on copper plates.


the science museum (london) has robert s 20-inch reflector.








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