Astrophotography

The Universe – My New Favorite

For many years, nature photography was my way of capturing special moments—landscapes, wildlife, macro worlds, and quiet places far removed from everyday life. With astrophotography, that perspective eventually expanded from the earthly realm to the depths of the universe.
Astrophotography ideally combines my enjoyment of technical challenges with a sense of awe at the boundless expanse of the universe.
Clear nights under the open sky bring a sense of calm, while the precision required to operate the astronomical equipment compels me to set aside the thoughts of everyday life.

And when the data I have gathered finally comes together on the computer to form a beautiful astrophotograph, I feel a great sense of joy once again.

Architecture of the Universe

A precise blueprint lies behind the universe. From the smallest building blocks to the largest known dimensions, the structure is as follows:
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  • Microcosm and Stars
    The fundamental building blocks are atoms, which form gas and dust. From these, gravity creates stars, which in turn are often surrounded by planetary systems.
  • Star clusters and galaxies
    Stars clump together to form open or globular clusters. Billions of these stars make up a galaxy (like our Milky Way).
  • Local Groups and Superclusters
    Galaxies are rarely isolated. They form small groups (like our Local Group) that come together to form huge superclusters.
  • Filaments and voids
    If you look at the cosmos as a whole, its structure is reminiscent of a huge sponge. The cosmos is compared to a sponge because the matter (galaxies and galaxy clusters) is not evenly distributed. It forms a network of fine threads and flat walls (the so-called filaments). In between there are huge, almost empty regions (the Voids). Just like a sponge, solid matter alternates with empty cavities.

    Filamente Voids

    On the largest scales, space resembles a gigantic, porous web (graphic created on a supercomputer).

    There is far more to the universe than the eye can perceive. The majority of matter and energy in the universe consists of attractive dark matter and repulsive dark energy.
    matter energy matter split However, their true nature remains a mystery. These seemingly massive structures account for only a fraction (approx. 5%) of the universe.

    The large-scale composition breaks down as follows:
    • Ordinary matter
      Ordinary matter is anything that has mass and occupies space. It makes up everything we can see and touch: planets, stars, and dust clouds, as well as us humans. Across the entire universe, this "normal" matter accounts for an estimated 5% of the cosmos. Chemically speaking, it consists of approximately 75% hydrogen and 24% helium.
    • Dark matter
      Dark matter (approx. 26%) is an invisible form of matter in space that neither emits nor reflects light. Although we cannot see it, it reveals itself through its gravity, which acts like an invisible glue. It serves as the "scaffolding" that holds galaxies together.
    • Dark energy
      Dark energy (approx. 69%) is not matter, but rather a type of repulsive force that acts throughout empty space. It is the reason why the universe is expanding—and why that expansion has even been accelerating for the past few billion years.
    We cannot directly handle the phenomena of dark matter and dark energy in the laboratory. Nevertheless, physicists are certain that they must exist.
    When we put together our mathematical models, our physical laws (such as Albert Einstein's general theory of relativity), and our observations of the universe, much of the mass and energy is missing to explain the movements of stars and the expansion of the universe. Without the concepts of dark matter and dark energy, our current science would not be able to explain the universe.

    The Age of the Universe: Big Bang and Hubble Constant

    Immediately after the starting signal, ...
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    Immediately after the starting signal—the so-called Big Bang—space expanded explosively from an infinitely small, hot point (the singularity). The universe did not originate like a conventional explosion within pre-existing space.

    Cosmological research estimates the age of the universe at approximately 13.8 billion years.

    Since the Big Bang, the universe has been expanding at a specific rate known as the Hubble constant (Hubble-Lemaître law).
    The Hubble constant indicates how much faster a galaxy is receding from us for every megaparsec (approximately 3.26 million light-years) of distance. It is central to determining the age of the cosmos.

    Wikipedia: Big Bang
    Wikipedia: Hubble's law
    Wikipedia: Georges Lemaître

    The three steps to determine the Hubble constant

    This illustration shows the three steps astronomers used to determine the expansion rate of the universe with unprecedented accuracy. By improving and refining the so-called cosmic distance ladder, the overall uncertainty of the measurement was reduced to just about 2.3 percent. The cosmic distance ladder is used to determine precise distances to nearby and distant galaxies.
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    Hubble Constant NASA

    Step 1: Cepheids and the parallax method
    The first step is shown on the left side of the image. Astronomers use the NASA/ESA Hubble Space Telescope to measure the distances to pulsating stars known as Cepheids. In doing so, they employ parallax—a fundamental geometric method in which a star's apparent position shifts slightly due to Earth's motion around the Sun.

    See also Star Clusters and Asterisms / Distance of the stars from Earth / Trigonometric parallax measurement on this website
    Stars and Star Clusters / Distance of Stars from Earth / Trigonometric parallax measurement
    on this website.
    Measuring these tiny positional shifts is extremely challenging. The observed changes correspond roughly to the apparent size of a grain of sand at a distance of 160 kilometers.

    The current Hubble study is based on eight newly analyzed Cepheids in our Milky Way. These stars are located at distances of approximately 6,000 to 12,000 light-years and are about ten times farther away than Cepheids whose parallaxes had been measured previously. Because they are very similar to Cepheids in other galaxies, they provide a crucial basis for calibrating the cosmic distance ladder.

    Once the true luminosity of a Cepheid is known, it can serve as a cosmic standard candle. A special property of these stars aids in this: the pulsation period is directly related to their luminosity. The more slowly a Cepheid pulsates, the brighter it is. By comparing its actual and observed brightness, its distance can be precisely determined.

    Step 2: Calibration of Type Ia supernovae
    In the second step, astronomers turn their gaze to nearby galaxies outside the Milky Way. There, they search for Cepheids in galaxies where a Type Ia supernova has recently been observed.

    Type Ia supernovae are excellent additional distance indicators because they reach nearly the same peak brightness. Using previously calibrated Cepheids, astronomers first determine the distance to the respective galaxy and can then derive the actual luminosity of the supernova observed there.

    Step 3: Measuring the expanding universe
    In the third step, Type Ia supernovae in very distant galaxies are studied. Unlike Cepheids, these stellar explosions are so luminous that they can be observed across distances ranging from hundreds of millions to billions of light-years.

    By comparing their actual and apparent brightness, astronomers determine the distance to these galaxies. At the same time, they measure the redshift of their light—the lengthening of light wavelengths caused by the expansion of space.

    By combining distance and redshift, it is possible to calculate how fast the universe is expanding today. This value is known as the Hubble constant and is one of the most important quantities in modern cosmology.

Astrophotography for Everyone

What was once reserved for large observatories ...
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What was once reserved for large observatories is now possible from a balcony or garden thanks to modern technology. Even the faintest structures of the universe can now be made visible with affordable equipment.
The universe is so vast that the light from many stars hasn't yet reached us. Therefore, we only see a small part of it from Earth.

The reasons for this are:
  • The distance of the stars
    Many stars are located at enormous distances from Earth, and light takes time to travel these distances. The farther away a star is, the longer it takes for its light to reach us.
  • The expansion of the universe
    The universe is expanding, which means some galaxies are moving away from us. This can cause light from those galaxies to be redshifted and take longer to reach us. When scientists talk about the expanding universe, they mean that it has been growing ever since its beginning with the Big Bang.
    The galaxies outside of our own are moving away from us, and the ones that are farthest away are moving the fastest. This means that no matter what galaxy you happen to be in, all the other galaxies are moving away from you.
    However, the galaxies are not moving through space, they are moving in space, because space is also moving.
    In other words, the universe has no center; everything is moving away from everything else.

    If you imagine a grid of space with a galaxy every million light years or so, after enough time passes this grid will stretch out so that the galaxies are spread to every two million light years, and so on, possibly into infinity.
  • Age of the universe
    The universe has a certain age (about 13.8 billion years), and there are stars whose light simply hasn't had enough time to travel to us.
  • Dust and gas
    Meanwhile, interstellar matter such as dust and gas can scatter or absorb light on its way to Earth, which can also prevent us from seeing the light from certain stars.
  • Limits of observation
    There are technical and physical limitations to our observations. Some stars are simply too faint or too distant to be seen with our current telescopes.
Because faint stars and astronomical nebulae emit only a small amount of light, their light must be captured in numerous individual exposures to produce a high-contrast, high-detail astrophotography image. This process can take several nights.
The light from the individual shots is then added together on the computer using special software, for example PixInsight.

The following images were taken with special astro cameras, telephoto lenses with focal lengths between 100mm f/2.8 and 500mm f/4.0, a Newtonian telescope Takahashi Epsilon130 and a  8” Ritchey-Chretien Telescope.  

To compensate for the Earth's rotation during long exposure times, the telescope/lens must track the stars very precisely. This is done with a special motorized device, see Wikipedia Mount. 

For observing and photographing the stars, a dark location with little light pollution is ideal, see Light pollution map.

A journey through space aboard a virtual spaceship
To mark the anniversary of the launch of the NASA/ESA/CSA James Webb Space Telescope, ESA presented a fascinating compilation of breathtaking space images.

Fauna