ALL ABOUT NIGHT PHOTOGRAPHY AND PHOTOGRAPHY OF STELLAR SKY
There are two main approaches to night photography:
1) shooting static stars, when in the final image we see them the same as our eye perceives them – as a set of points in the sky;
2) shooting of tracks using very long exposures, in which the photo captures the trajectory of stars in the sky around the South or North Pole of the world.
Let’s analyze each of them in more detail …
Shooting static stars
In astrophotography, to obtain images of static stars, star clusters, galaxies, nebulae, and others, such a device as a parallax mount with the possibility of guiding is used. Parallactic is such a mount, one of the axes of which can be installed parallel to the axis of the world, directed to the North Pole. Guiding is the process of monitoring and correcting the tracking of a camera or telescope for the movement of celestial objects – usually as a result of daily rotation of the sky – during exposure.
Of course, all this is very interesting, but for some reason it seems to me that most ordinary photographers do not have such special devices, so in this article we will consider shooting only with a simple tripod, and someone who is interested in astrophotography will easily find a lot of information on this topic. in the Internet.
So, what do we need to know in order to take a picture with a static, no tracks, starry sky? The most important thing is to memorize a simple rule 600, which is as follows: if you divide 600 by the focal length of your lens (equivalent to a 35 mm camera), then we get the maximum shutter speed at which the stars in the sky look like dots rather than dashes. So, for a 15 mm lens, the maximum shutter speed when shooting static stars will be 600/15 = 40 sec., And for a 50 mm lens – 600/50 = 12 sec.
Based on this rule, we expose the obtained exposure in the camera and, if possible, leave the aperture as open as possible, which would give an acceptable picture quality. Now we just have to pick up the value of the photosensitivity, in which we get a balancedly exposed image.
Note. Blocking a mirror can significantly increase the sharpness of exposures comparable in duration with the positioning time of a mirror (from ~ 1/30 to 2 seconds). On the other hand, the shaking of the mirror is negligible for exposures whose duration is much longer; As a result, blocking the mirror in most cases is not critical when shooting at night.
Shooting the rotation of the starry sky requires the longest shutter speeds – from 10 minutes to several hours, depending on the focal length and how long the trajectories you want to get in the picture. The exact value of the extract is difficult to calculate, it can be determined only on the basis of his personal experience and preferences for the length of the tracks. For example, I know that a 50-mm lens for beautiful, for my taste, tracks needs an exposure of 20–40 minutes, a 24-millimeter – about 90–120 minutes, and so on.
There are two main approaches to shooting similar subjects:
1) shooting one frame;
2) shooting a continuous series of images with their subsequent stitching in specialized software.
Until recently, almost all photographers who wanted to capture the circular rotation of the stars in the picture used exactly the first method. I highly recommend the second option. But so that you yourself can decide what is preferable for you, let’s analyze all the disadvantages of the first and the advantages of the second approach.
So, the disadvantages of shooting one frame:
the difficulty of calculating the correct expopairs, in which the picture would be worked out in a balanced way both in the shadows and in the light. It is sad to find an overexposed or underexposed image even after half an hour of exposure, not to mention exposures lasting several hours;
when using even the most modern digital technology, with super long exposures, strong, sometimes unbearable digital noise appears in the photographs (even at relatively low ISO values);
high risk of shake-ups at such long exposures;
if you do not notice in time how your front lens has sweated up, write down.