What is Astrophotography and Deep Sky Cosmic Beauty

Astrophotographers Yuri Zvezdny and Oleg Milantiev told National Geographic how photography of deep space objects differs from ground photography in its usual sense.

Astrophotography is the art of taking photographs of space objects: planets, comets, stars, nebulae, artificial satellites, galaxies - in a word, everything that is outside the atmosphere of our planet. There are several directions in astrophotography: lunar-planetary photography, night landscape photography and astrophotography of deep space objects. The differences between them are very significant. We will not go deep into the details of each type of shooting, but touch on one promising direction - collective astrophotography.

Photography of deep space objects is very different from ground photography in its usual sense. Space objects are too dim, and very little light comes from them, so astrophotographers often cannot do with one shot to create the final image. To obtain clear and low-noise images, you have to take dozens, and sometimes hundreds of frames with shutter speeds of 5, 10, 20 (and more) minutes each. Then these frames are averaged among themselves in special programs. This allows new details to be revealed on the subject. See how stacking frames helps a lot:

The first image is a single 15-minute frame of a dusty nebula in the constellation South Corona, and the second is a processed photograph of thirty such frames. Note how much more detail can be discerned in the summary photograph.

A large number of special equipment is used to obtain such images. This is a laborious and time-consuming process both at the shooting stage and at the processing stage.

The weather factor is very important. There are not so many clear nights in central Russia. Moreover, the nights should be moonless, since the moon strongly illuminates the sky and interferes with filming. It turns out that even with the best equipment it can be very difficult to collect enough exposure. And this is where the collective approach comes to the rescue.

Its essence is simple: astrophotographers join their efforts and jointly shoot any single object. The resulting material is then sorted, leveled and calibrated. The output is a raw summary image (you can say Raw), in the final processing of which anyone can try their hand. This approach speeds up business many times over and increases work efficiency. In a relatively short period of time, as much material can be collected as it would take years to collect alone.

One of the first successful collective Russian projects of the international level - shooting the galaxy M51 "Whirlpool" in the constellation "Hounds". During the implementation of this project, about two hundred hours of exposure were accumulated!

This is an astounding value and a great achievement. No less time was spent on structuring the received data and withdrawing the final amount.

Now we have considered the case when photographers agree in advance about the shooting of a particular object. But another approach is also possible, when existing data is used to create the final images. To do this, the collection of data on an object is announced, and everyone who has ever filmed it, send their sources. Next, the final amount is prepared from the source. For example, this is how a collective photo of the M101 "Pinwheel" galaxy was taken in the constellation Ursa Major.

To create this image, photographs were used by the participants at different telescopes from 2011 to 2016, and the total exposure was 76 hours.

You may ask: Does the data become out of date over such a long period of time? In the case of deep space objects, almost never. Galaxies are so far away from us and they are so large that it will take more than one thousand years to notice at least some changes in their shape and structure.

In the process of implementing such projects, a large role belongs to the coordinator. It is he who collects, structures and performs the initial processing of a huge amount of data, the account of which goes to hundreds of gigabytes. This is a titanic job, fraught with many difficulties. We have to combine and scale very dissimilar images taken with different cameras on different telescopes with different focal lengths. Also, not all frames used for the summary image are perfect. Some of them contain defects that may appear in the final photograph. To prevent this, it is necessary to programmatically correct errors in shooting and calibration.

More recently, a group of Russian astrophotographers has implemented another collective project. After lengthy discussions, a rather difficult target was chosen - the galaxy M94 from the constellation "Dogs Hounds". The material on this galaxy has been collected for several months. During this time, almost 200 hours of exposure were accumulated. Telescopes with an objective diameter of 200 to 500 mm and a focal length of 1000 to 4080 mm were used. In total, ten astrophotographers took part in the shooting process: Kirill Averin, Nikita Kozlov, Nikita Shamorgin, Yuri Toropin, Vladimir Vavin, Vitaly Archugov, Alexei Naletov, Evgeny Buklikov, Vladimir Ilyin and Oleg Milantiev.

The final assembly was handled by Oleg Milantiev. After all the efforts, the final amounts were made available for free. Anyone could try to process such fantastic material. The undoubted advantage of collective astrophotography is the availability of Raw-sums for anyone. This gives rise to many options for processing the source material. One photographer, for example, wants to sharpen the center of a deep sky object. The other, on the contrary, seeks to show the large-scale structure of the outer arms of the galaxy. And the third is more interested in the shape, color and light of the stars.

Collaborative photography opens up new perspectives in astrophotography. New technical capabilities, joint developments and experience in combining images obtained from different telescopes help to see space objects much more clearly, and collective space exploration raises amateur astrophotography to a high level previously available only to professionals.