If you haven’t heard about the Large Synoptic Survey Telescope (LSST), it’s basically a wide-field survey reflecting telescope and also the world’s largest digital camera, with an 8.4-meter primary mirror, currently under construction, that will photograph the entire available sky every few nights. A 3.2-gigapixel prime focus digital camera will capture a 15-second exposure every 20 seconds. The 15-second exposures are a compromise to allow spotting both faint and moving sources, with each spot on the sky is imaged with two consecutive 15 second exposures, to efficiently reject cosmic ray hits on the CCDs. Gizmodo recently got the chance to get up-close with the telescope on the El Peñón peak of Cerro Pachón, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile. The site construction began on April 14, 2015, with engineering first light anticipated in 2019, while science first light in 2021, and then full operations for a 10-year survey beginning some time in January 2022. Read more for two more videos and additional information.
This massive camera includes a filter located between the second and third lenses, as well as an automatic filter-changing mechanism. Despite boasting six filters covering 330 to 1080 nm wavelengths, the camera’s position in front of the mirror limits the size of its filter changer. It’s capable of only holding five of them at a time, therefore one of the six must be chosen to be omitted each night.
“You might wonder what makes this behemoth a ‘digital camera.’ It helps to break a digital camera into its component parts: a lens directs light onto a sensor, turning the light into an electrical signal and then into data stored on a computer. Your iPhone’s camera sensor is somewhere around 7 or 12 mega, or million, pixels, while a DSLR can have somewhere from 18 to 50 megapixels. The LSST will have 189 16-megapixel chips, all aligned on a perfectly flat plane,” said Gizmodo.