Have you ever been intrigued by night photography or astrophotography? Here is a guide that will help you understand a little more about this subject.
At least once in our life each of us has tried to capture the fantastic stellar landscape suspended over our heads. Those who have made more than one attempt, with a mobile phone or a camera, will probably have been disappointed: poorly defined images, busted displays and photos only to trash are often the results that are obtained. This is because, to the detriment of what one might think, the night photography and the astrophotography they are difficult to master, even for the most expert “earthly” photographers.
Do not worry, with a little attention and a good dose of patience you can get good results even with home or entry-level equipment, without necessarily paying out capital in cutting-edge equipment.
Given the complexity of the topic, we split this guide into two parts. In this article we will talk about the introductory notions, in the next, we will go deeper into the practice.
The basics of photography
If you start from scratch it is right that you highlight at least the most useful basic photographic notions in the field of night photography. First of all, you need to understand how a camera is built-in broad terms – (whether it is an SLR or a camera of a telephone) the process is almost identical) and know that at least there are three basic elements that you need to know: the ISO sensitivity given by the sensor, the diaphragm and the shutter.
The Sensor is a small shiny parallelepiped and is located in the heart of the cameras and our smartphones positioned immediately after the lenses. Its function is to transform (thanks to photodiodes) any light signal into an electrical signal, which then the software will translate into an image (a typical JPEG photo for example) or into a raw data package (called a RAW file).
The sensor then acts like our retina, which picks up the signal of the surrounding world allowing you to process it in your brain. A fundamental aspect of the sensor is the ability to set its sensitivity to light, making it more or less responsive to the signal. In this case, we speak of ISO values and generally the higher they are (ISO 6400, ISO 16800, going up) and the more they easily impress the light – however giving more “digital noise” as you go up.
The Diaphragm it is comparable to our Iris and Pupil: the more dilated it is, the bigger it is (take for example the eyes of cats)
and more light can enter. It is one of the fundamental components in that it can be modified by the user himself according to his needs, and hides in its use some “consequences” that represent the ABC of the photographer (like the blurry effect and the choice of depth of field – but for now let’s focus only on its primary role).
When we talk about the diaphragm we often notice the words “f / 2.8”, “f / 4”, “f / 10” and so on: they are the so-called STOP and – said very simply – are the various degrees of exposure that a given lens allows. To be really precise, they actually indicate the “focal relationship” of a goal, but it would not be wise to go into other notions when there is so much essential to say; professional photographers or great lovers of photography don’t want it for this rather simplistic explanation but, in simple terms, the important thing to remember is that the smaller the number after the f, the more we are allowing the light to enter.
L’Shutter instead it is to be considered as a real human eyelid. It is a mechanical part in the shape of a “damper” that the more it remains open and the more it leaves the sensor exposed to the external light signals. Also, this part is manually adjustable and, thanks to it, many combinations can be invented depending on the opening time that is imposed: for example, a shutter that snaps into a 1/2000 of a second it is so fast that it allows you to imprint a very “elusive” image on the sensor, like maybe the racing car or a cyclist in curves, even showing static wheels. If instead, we lengthened the times, perhaps bringing the speed to 1/30 of a second then we could have difficulty in framing a still subject, because such a slow and sensitive time would be affected even by the micro-movements of the human body, making the photo appear blurred.
Keeping a shutter open very long allows us to do “long exposure photo“, that is a photo that continues to pick up a light signal and to superimpose a signal over a signal (one could say that it is like a video with the big difference, however, that each frame is not sequential to the other, but superimposed on the previous one).
Difference between Night Photography and Astrophotography
One of the other fundamental things to know is the difference between night photography and astrophotography and above all to know which one you want to dedicate yourself to. Although they may look similar in reality there are more differences than similarities: the first – also called “landscape night” – is limited to framing an earthly landscape, with natural or artificial elements, and then trying to make the celestial vault protagonist, often giving greater emphasis to the Milky Way (and in particular to its core, which is very well visible to us throughout the summer).
Astrophotography, on the other hand, focuses more on the deep sky (“Deep Sky” in English) or on all those objects that are almost impossible to see with the naked eye (some of the extraordinary beauty) if not in some really dark sky.
Often it requires not only photographic equipment of a certain level, but also certain support telescopes and “frames” that can allow even session hours while always keeping our target in the frame. But the latter branch, being the most complex, we will deal with it later. Now let’s focus our basics on night photography.
Know our subjects
The stars, cosmic objects of unimaginable power, capable of telling us the darkest secrets of the entire universe, are actually really elusive subjects. In fact, how many times have we seen only a few or none even with a clear sky? This is due to two factors, one natural and one unfortunately of an anthropic nature: Apparent Magnitude and Light Pollution.
NASA, Stanley Kubrick and the multimillion-dollar target One of the brightest lenses in the history of photography has a value of f / 0.7 and was created specifically for the Apollo program in 1966 by the Carl Zeiss company. The aim was to take very bright and detailed photos of the lunar surface from the various orbiting probes. The even more curious thing is that only ten specimens were built: six went to NASA, one to Zeiss himself and three were bought no less than by director Stanley Kubrick, who used them for his wonderful Barry Lyndon, in particular for a scene that the director dictated that it should be done only and exclusively by candlelight and that therefore required objectives out of the ordinary. The value of this goal? Not much, just $ 23 million. Each.
Their Apparent Magnitude it is, without too many turns of words, a scale that allows you to indicate how bright an object observed from Earth is. The lower the number (often even with negative values), the more intense the brightness and consequently the more it will be easily detectable, even with the naked eye.
For example, the brightest star in our firmament is Sirio and has an “MA” of -1.46. It is enough for us to know for now that in general the human eye, without any kind of visual problem or impediment – and assuming that you are not equipped with these – is able to recognize objects that go below the value +5 or +6. It would seem in reality a rewarding value given that hundreds of thousands of celestial bodies are gathered in it, but then why is there no real response in our skies? Unfortunately, the human factor comes into play here.
Light pollution it is probably the biggest plague that grips astronomers, Astro-amateurs and photographers. It can be measured in various ways (Radiance, Magnitude per arc second), and its effect is more than tangible, so much so that often just having a “look” at the area to understand what situation you are in. It is mainly caused by all that artificial light radiation which is dispersed in some way and which inevitably reflects in our atmosphere and on our clouds.
The whole sky then becomes brighter, inevitably covering the weaker stars. LEDs, parasitic lights, neon lights and headlights projected directly into the sky are among the worst causes that contribute to the increase of IL, and although our country is not one of the largest, let alone one of the most populous, it is actually one of the most affected by this problem due of its morphology and its demographic distribution. Throughout Italy, it is estimated that there are not more than a handful of areas where you can enjoy a truly dark sky.
Fortunately for us, an average dark sky will be enough to start, and you can be satisfied with the rural areas outside the big cities or better still with the mountain villages. Altitude also plays a fundamental role, the higher you are, the better the air quality will be. To know under which sky we live, without necessarily having to equip ourselves with particular instruments, we can rely on our eyes and the precious “Bortle scale“.
La Scala Di Bortle
The Bortel staircase was created in 2001 by John E. Bortle just to come to the rescue of beginners and budding amateurs, in order to give a hierarchical classification of their celestial landscape.
It is divided into nine sections with level 1 representing the “perfect” sky (in Italy it is not reflected) and where the only source of light should be that of the Milky Way itself until gradually reaching level 9: the typical sky of urban centres larger, in which even the brightest and most famous constellations are hidden. Unfortunately in our beautiful country there are very few and very rare level 2-3 zones, and often found in the high mountains (not easily accessible), so you have to settle for what you have. To start – as we mentioned earlier – even a level 4 or 5 skies would be fine, as long as you don’t expect who knows what miracle, but we assure you that with the right precautions and with a good dose of practice you will be satisfied with your work, even in non-ideal conditions.
Furthermore, it should be remembered that the staircase is very useful and almost always reliable, but is based exclusively on personal empirical observations, it can happen that a place praised as amazing can then prove to be poor: clouds, humidity, high and low altitude air jets can make a lot of difference, therefore, before starting with the exasperated hunt for the best sky, you have to start with the simplest you have at hand and from then on build your own castle of experiences.
There have been many preliminary talks, and if you have followed us so far it means that perhaps your interest is more noble and ardent than you think, here we invite you to keep yourself ready and to assimilate these basic notions as well as possible. The boring part is probably over, we will return soon with the second part of this guide, venturing – finally – in some practical and technical tests: stars, here we come!