The Largest Digital Camera

A Ten-Year Film of the Sky

At the end of June 2026 the Rubin Observatory began its ten-year Legacy Survey of Space and Time (LSST). The telescope stands on Cerro Pachón in Chile, 2,647 m up, and takes about 700 exposures a night, a new image about every 40 seconds. The main survey covers about 18,000 square degrees of the southern sky, each patch about every three days.

Over ten years each patch is photographed about 800 times across six colours. Line up the images of one patch in time and you have a time-lapse film of the sky: whatever moves or brightens shows. Each night brings about 10 TB of data.

began June 2026 · ten years · each patch about 800 times · about 700 exposures a night

The Size of a Small Car

The LSST Camera is 1.65 m across and 3.73 m long and weighs about 3 tonnes (published figures run from 2,800 to 3,060 kg): the size of a small car. Guinness World Records lists it as the largest digital camera. It was built at the SLAC National Accelerator Laboratory in California.

Here a quarter is cut away at the front and top; the cut is painted red. From the front: the first two lenses, the filter changer, the carousel round the cryostat, the focal plane inside the cryostat, and at the back the utility trunk with its electronics and lines. Beside it stands a person in a clean-room suit, 1.75 m tall.

1.65 m across · 3.73 m long · about 3 t

Wide, Not Zoomed

This camera does not magnify more than other telescopes. Its strength is a wide field: one image covers 9.6 square degrees, 3.5° across, the area of about 45 full Moons and seven Moons wide.

Multiply that field by the 8.4 m mirror (about 6.5 m effective) and the product of light-collecting area and field is 319 m² deg²; the Sloan Digital Sky Survey has 5.9. So it covers the visible southern sky in three or four nights. How sharp the images are is set by the air: stars there are typically about 0.7″ wide, a pixel only 0.2″.

9.6 deg² · about 45 full Moons · 319 m² deg²

189 Sensors

The focal plane is 0.64 m across and carries 189 science CCDs, each 4,096 × 4,096 pixels; a pixel is 10 µm wide, 0.2″ on the sky. Nine CCDs make a “raft”, and 21 rafts stand in a square; four more rafts in the corners carry the sensors for guiding and for measuring the wavefront.

The 189 CCDs hold about 3.2 billion pixels (this page’s arithmetic: 189 × 4,096²). They come from two makers, and all nine in a raft from the same one. The whole focal plane is flat to within a tenth of a hair’s width. Each CCD has 16 outputs, and all of them read at once.

189 CCDs · 21 rafts · about 3.2 billion pixels · 10 µm pixels

Colder Than −100 °C

The CCDs sit in the cryostat, a cold vessel pumped to a vacuum of about 10⁻⁷ Torr, with L3 as its window. The design temperature is about −100 °C; a 2026 paper reports the focal plane run at 150 K, about −123 °C. The cold keeps down bright defective pixels: the warmer silicon is, the more charge it makes on its own.

The cooling uses a mix of ten liquids and gases. Behind each raft are its readout boards, also inside the cryostat and designed to work at about −10 °C. The lines leave through the back of the cryostat into the utility trunk.

design about −100 °C · run at 150 K · about 10⁻⁷ Torr

Cut Open: Three Lenses

Starlight reflects off the primary, secondary and tertiary mirrors and arrives already converging, then passes three fused-silica lenses. L1 is 1.57 m across, believed to be the largest high-performance optical lens ever made; L2 is 1.10 m; L3 is about 0.7 m across and about 6 cm thick, and is also the cryostat’s vacuum window, just 2.85 cm from the focal plane.

The three lenses do not magnify. They correct the colour errors that a thick window brings and flatten the image, so that the flat focal plane is sharp everywhere. The rays drawn here are schematic and leave out the bending inside the lenses.

L1 1.57 m · L2 1.10 m · L3 about 0.7 m · 2.85 cm from the focal plane

Six Colours, Five Slots

The CCDs record only brightness, not colour. Colour comes from the filters: u, g, r, i, z and y, from the ultraviolet through visible light to the near infrared, together 320 to 1,050 nm. Each is 75 cm across and weighs 25.5 to 38 kg, with about 100 coating layers a surface that pass one band and reflect the rest.

The carousel inside the camera holds only five; six is “geometrically impossible”: the five sockets stand in a pentagon round the cryostat. The sixth waits outside the camera and is swapped in by day with a loader, about every few weeks.

u g r i z y · 320⁠–⁠1,050 nm · 75 cm and 25.5⁠–⁠38 kg each

A Filter in Ninety Seconds

To change colour, the carousel turns the chosen filter to the stand-by position at the top; the auto-changer takes it out of its socket and sets it in the beam to within 100 µm. It takes under 90 seconds, up to 40 times a night.

The real path is a complex three-dimensional one, drawn here as a simple curved rail. Once the filter is in place, the light that crosses it keeps only its band.

under 90 s · placed to 100 µm · up to 40 a night

Thirty Seconds, Then Move

A “visit” is one 30-second exposure (38 s in u). The shutter’s two halves slide apart and close again, each in about a second. The original design was two 15-second exposures; after commissioning it became one.

With the shutter closed, every pixel is read out: 2 s by design, slowed to about 3 s for lower noise. Meanwhile the telescope swings to the next patch, in a median 4.8 s. So a new image arrives about every 40 seconds.

expose 30 s · read about 3 s · slew 4.8 s · an image about every 40 s

Alerts Within a Minute

Each new image is compared with earlier images of the same patch, and anything that has brightened, faded or moved makes an alert. The design calls for 98 % of alerts out within 60 seconds of the readout, at least 10,000 a visit on average and 10 million a night over the long run; the observatory now expects about 7 million a night. The alerts are public worldwide and sorted by seven automated “broker” systems.

When the First Look images came out in June 2025, about 10 hours of observing had found 2,104 asteroids never seen before, 7 of them near-Earth asteroids, none dangerous. Over ten years the survey expects to catalogue about 6 million Solar System objects and see about 10 million supernovae.

98 % within 60 s (design) · about 7 million a night · 2,104 new asteroids in 10 hours

Stretched a Little

Light from distant galaxies is bent by the gravity of the mass in front of them, and each galaxy is stretched a little: weak gravitational lensing. One galaxy shows nothing, because galaxies come in many shapes, scattered by about 0.26 in each direction. By this page’s estimate, seeing a 1 % stretch takes about 680 galaxies averaged together.

So it is statistics: the survey will measure the shapes of about 2 billion galaxies and work out how matter, most of it unseen dark matter, is spread and how it has gathered over time. The observatory is named after Vera Rubin, whose measurements of how galaxies rotate gave strong evidence for unseen matter. For a dark-matter detector underground, see the plate “Hunting Dark Matter”.

shapes of about 2 billion galaxies · σₑ = 0.26 · a 1 % stretch takes about 680 galaxies

From California to the Andes

The camera was built at SLAC in California. The focal plane was finished in January 2020, and that September it took the first 3,200-megapixel photos: with no lenses yet, a 150 µm pinhole projected the images, among them a head of Romanesco. The camera was completed in April 2024 and shipped to Chile in May.

In March 2025 it was lifted onto the Simonyi Survey Telescope; on 15 April it first looked at the sky, and on 23 June the First Look images were released. The ten-year survey began on 29 June 2026. For an infrared telescope in space, see the plate “The Webb Space Telescope”.

first 3,200-megapixel photos 2020 · completed 2024 · first sky 15 April 2025 · survey from June 2026

Taken Apart

The camera body, the front lenses, the auto-changer, the shutter, the carousel, the cryostat and the utility trunk come apart one by one.

Point at a part (tap it on a phone) and it lifts on its own, with its name; the rest fade.