Me vs the world's largest digital camera
Me vs The World’s Largest Digital Camera
For me, the most exciting astronomy news of 2025 was unveiling of the the world’s largest digital camera. The Vera Rubin Observatory, the world’s newest giant telescope, clicked and released its first image using this camera in June earlier this year. It captured a spectacular part of the Milky Way’s core that houses two celestial jewels—The Lagoon and Trifid Nebulae. The image, as expected, was eye-catching. But to my surprise, it looked eerily similar to a picture I had taken myself using a small canon mirrorless camera just a month before that.
Sit tight to see a side-by-side comparison later, but does it really matter which picture looks better? What’s more interesting (in my opinion) is the fact that that these two instruments can play in the same field at all.
To the left is Vera Rubin’s humongous 3200 Megapixel (or 3.2 Giga-pixel) camera. On the right is my humble entry-level 24.1 Megapixel Canon M50 mirrorless camera whose image sensor is smaller than a postage stamp. Rubin’s, on the other hand, is the size of a large pizza.
So how is my small camera able to “see” the same view as one of the world’s largest telescopes?
Scopes vs Cams
Telescopes are built to magnify stuff. They gather lots of light coming in from very far away, and focus it down to a small area using using concave mirrors or convex lenses. An eye-piece or a camera sensor placed in this small area then enables us to see a tiny part of the sky enlarged many times over. The degree to which a telescope can magnify things is determined by how much larger in area the main light-gathering unit (the primary mirror or lens) is compared to the size of the eye-piece or the camera sensor where the final image is made. The primary attribute of a telescope that sets this magnification is its focal length, or the distance from the lens/mirror where the light converges to form an image.
Cameras, on the other hand, are built to capture everyday life such as landscapes and parties and portraits. They can magnify stuff too—you just need to put on a large telephoto (or zoom) lens which has a long focal length. Similar math applies here: longer the focal length, greater the magnification. The lens I used for my picture of Lagoon/Trifid was a Rokinon 135mm—the largest focal length lens in my armory*. This lens essentially telescopifies my camera to the furthest extent my money can buy.
For astrophotography, wide lenses with short focal lengths are perfect to capture the band of the Milky Way stretching across the sky. Narrow, long telephoto lenses like my 135mm lens allow me to click Moon pictures, or close-ups of objects like the Andromeda galaxy or the Orion nebula.
But if you want to do research and peer really deep into what goes on in a nebula or distant galaxies, you really need a telescope that resolves very narrow parts of the sky in exquisite detail. The focal lengths of space telescopes like JWST and Hubble are ginormous, at 131.4 and 56.7 meters respectively. That’s almost a thousand times longer than my largest lens. This allows them to magnify galaxies billions of light-years away, and peer deep into cosmic history.
With this comes a trade-off: they can only view a teeny tiny part of the sky at a time. JWST’s first image, which contained dozens of galaxies stretching all the way towards the edge of the visible universe, was only as big as a grain of sand held at an arm’s length in the sky. Ground-based giant telescopes such as Subaru Telescope on Mauna Kea, Hawaii or the Magellan Telescope in Chile also have long focal lengths measuring tens of meters.
Additionally, light coming from such faraway galaxies, or even relatively nearby nebulae is very, very, very dim. Collecting enough photons from these objects requires the telescope to do two things:
- Use a very wide or collecting mirror, similar to how a wider bucket catches more rainwater in a given amount of time than a narrower one. This has an obvious limitation as to how big we can build and polish shiny mirrors.
- Expose its camera for hours at a time—just like a bucket put out in the rain for longer collects more water.
Go wide or go deep?
Going deep lets you study one small thing really well. But the sky is huge. Ideally, one would like to use a wide-field lens to see more of it at a time.
This is where Rubin comes in.
Rubin’s view
Despite the size difference, it’s remarkable how closely this giant astronomical telescope functions like an astrophotographer’s camera. It even takes pictures in 30-second exposures, which is exactly the maximum limit my camera allows (telescopes normally expose images for hours at a time in order to collect more light and “look deeper” into the universe). Rubin’s action plan is to quickly sweep through photograph large swaths of the sky and make timelapse movies that can identify what all in the sky is changing: think nearby asteroids, variable stars, and exploding supernovae. But at the same time, it’s able to peer deep into