Asteroid making its closest approach to Earth this week

On 4 February, asteroid 2011 MD will make its closest approach to the Earth. Though it will not be visible with the naked eye, the asteroid will pass 15,000,000 km away from Earth—much closer than those in the asteroid ...

Astronomers discover first population of binary stripped stars

Astronomers at the University of Toronto have discovered a population of massive stars that have been stripped of their hydrogen envelopes by their companions in binary systems. The findings, published in Science, shed light ...

How can we bring down the costs of large space telescopes?

We're all basking in the success of the James Webb Space Telescope. It's fulfilling its promise as our most powerful telescope, making all kinds of discoveries that we've been anticipating and hoping for. But the JWST's story ...

ESO's Extremely Large Telescope is now half completed

The European Southern Observatory's Extremely Large Telescope (ESO's ELT) is a revolutionary ground-based telescope that will have a 39-meter main mirror and will be the largest telescope in the world for visible and infrared ...

Astronomers witness energetic switch on of black hole

A team of astronomers led by researchers from the University of Birmingham, University College London and Queen's University Belfast have discovered one of the most dramatic 'switches on' of a black hole ever seen. They will ...

Hawai'i observatories add color, depth to European Euclid mission

Launched on July 1, 2023, the European Euclid mission will observe billions of galaxies over one-third of the sky to create a map of the Universe. But Euclid's map will be in black and white; telescopes in Hawai'i, including ...

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Optical telescope

An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum for directly viewing a magnified image for making a photograph, or collecting data through electronic image sensors.

There are three primary types of optical telescope: Refractors (Dioptrics) which use lenses, Reflectors (Catoptrics) which use mirrors, and Combined Lens-Mirror Systems (Catadioptrics) which use lenses and mirrors in combination; for example, the Maksutov telescope and the Schmidt camera.

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