Stargazing in broad daylight: how a multi-lens telescope is changing astronomy

Astronomers from Macquarie University have developed a new technique for observing celestial bodies during the day, potentially enabling 24-hour visual monitoring of satellites and significantly improving safety on Earth and in space.

Their technique uses the university’s Huntsman Telescope, a unique array of ten camera lenses operating in parallel, originally designed for ultra-sensitive night sky observations.

In an article published in Publications of the Astronomical Society of Australia on May 20, researchers will demonstrate the Huntsman’s ability to accurately measure stars, satellites and other targets when the sun is high overhead, despite astronomers traditionally observing only at night.

‘People have been trying to observe stars and satellites during the day at optical wavelengths for centuries, but that has proven very difficult. Our testing shows that the Huntsman can achieve remarkable results in daylight,” said lead author and Ph.D. astrophysics. candidate Sarah Caddy, who helped design and build the Huntsman Telescope.

Caddy worked with a team of Ph.D. students and staff from Macquarie to deploy the Huntsman, which celebrated its official opening last year at the Siding Springs Observatory in Coonabarabran.

The telescope combines an astronomy camera and astromechanical focusing equipment with an array of 10 highly sensitive 400mm Canon lenses, aimed to cover the same patch of sky.

Because the sun blows away most of the light from other celestial bodies, astronomers rarely observe during the day, but Caddy and her colleagues tried special ‘broadband’ filters on a test version of the Huntsman telescope to block out most daylight while still allowing specific wavelengths from celestial bodies to pass through. to let. get through.

This test version, a mini-Huntsman pathfinder telescope with one lens, installed in the university’s observatory, allowed the research team to assess different settings in a controlled environment without affecting the Huntsman telescope.

Supernova approaching

The Huntsman’s daytime capability allows continuous monitoring of certain bright stars that may not be visible at night for months because they are too close to the sun.

An example is the red supergiant Betelgeuse, a nearby star about 650 light-years away in the Orion constellation in our Milky Way Galaxy.

Betelgeuse is of great interest to astronomers as the star dimmed significantly between late 2019 and 2020, likely due to large emissions of gas and dust.

“Without this daytime mode, we wouldn’t have any idea whether one of the brightest stars in the sky has gone supernova until a few months after the explosive light reached Earth,” said co-author Associate Professor Lee Spitler, Head of Space Projects at Macquarie’s Australian Astronomical Optics (AAO).

‘We know that Betelgeuse will explode ‘soon’ [in astronomical terms this means anytime between now and millions of years into the future]but not exactly when it will happen.

“For about four months of the year, it is only observable during the day, because the sun is between Betelgeuse and Earth at that time.”

Calibrate with Betelgeuse

The study confirmed that the Hunter’s daytime photometry data for Betelgeuse agrees with observations from observatories around the world, and even with space telescopes.

“This breakthrough paves the way for uninterrupted long-term studies of stars like Betelgeuse as they undergo powerful outbursts near the end of their lives, ejecting enormous amounts of stellar material in the final phase of the cosmic cycle of rebirth,” says Spitler.

“Astronomers love when stars in the Milky Way go supernova because it can tell us so much about how elements in the universe are created.”

Unfortunately, he adds, supernovae are relatively rare in the Milky Way; the last time this happened was in 1604.

“But when a supernova went off in a mini-galaxy next to our Milky Way in 1987, it was so useful to astronomers that they are still observing the expanding supernova explosion almost 40 years later.”

Preventing collisions

Mastering daytime observation also provides a major advantage in the rapidly growing field of space situational awareness (SSA), which involves accurately monitoring an ever-growing population of satellites, space debris, and other artificial objects orbiting the Earth. earth rotates.

More satellites will be launched in the next decade than in the entire history of human space exploration.

‘With approximately 10,000 active satellites already orbiting the planet and plans to launch another 50,000 satellites into low Earth orbit over the next decade, there is a clear need for dedicated day and night telescope networks to continuously track satellites detect and track,” says Caddy.

Potential satellite collisions have serious consequences for communications, GPS, weather monitoring and other critical infrastructure.

Satellite photometry – an astronomical technique that uses optical telescopes to study changes in the brightness of celestial bodies – can reveal valuable information, including the composition, age and condition of objects in orbit.

“Opening up to daytime observation of satellites allows us to monitor not only where they are, but also their orientation, complementing the information we get from radar and other monitoring methods, protecting us from possible collisions,” says Caddy.

Astro treats

Caddy’s team demonstrated the Huntsman’s potential for other astronomical observations requiring day and night coverage, including monitoring satellites.

The team used the mini-Huntsman to refine the techniques over many months, systematically examining factors such as optimal exposure times, observation timing and accurate tracking of targets even through atmospheric turbulence.

“Daytime astronomy is an exciting field, and with advances in camera sensors, filters and other technologies, we have seen dramatic improvements in the sensitivity and precision achievable under clear-sky conditions,” says Caddy.

Spitler adds: “We have refined a methodology for daytime observation and demonstrated that it can be done on affordable, high-quality equipment such as Canon lenses.”

The Huntsman is constructed so that its ten lenses work in parallel, feeding ten ultra-fast CMOS camera sensors that together can capture thousands of short-exposure images per second.

The connected camera can process images in no time and manage very large data streams, using robot control to track and capture fast-moving objects, and enable continuous 24-hour monitoring of objects.

“The fact that we can make accurate observations 24 hours a day overturns long-standing limitations on when astronomers can scan the sky,” says Spitler.

“Daytime astronomy will become increasingly important as we enter the next space age.”