Today we’ll discuss about choice of best objects for astrophotography according to your equipment. Astronomy lovers say: “There is no such photographer who would not dream of becoming an astrophotographer.” Indeed, although the process of visual observation is a special, incomparable pleasure, various reasons prompt people to take up astrophotography. Someone wants to share the beauty of the heavens with others, someone just wants to see more: after all, during visual observations, even the brightest and most interesting objects of deep space look ordinary-looking gray specks, and the dimmer ones are not visible at all. When photographing, even a small telescope will show them in color with details imperceptible to the human eye. And in the images of planets, you can often see more small details than visually. Experienced amateur astrophotographers get pictures as good as pictures from the Hubble Telescope.
Of course, in order to achieve significant results, there is not enough good equipment, and the subsequent processing of the obtained initial images plays an almost important role. But processing skills come with experience, and it is better to acquire a telescope for astrophotography right away. There are not so many clear nights to be wasted fighting the recalcitrant “iron”.
Who Are The "Planets" And "Deep Sky" Guys?
Usually astrophotographers specialize in types of photography as "planets" (shoot the moon and planets) or "deep sky" (shoot galaxies, nebulae, star clusters, comets, etc.). Depending on this, the equipment used, image processing methods differ, and the requirements for shooting conditions are often completely opposite. So, if for shooting planets and the Moon you need a calm atmosphere (even if it is not very transparent), the so-called "sing", then transparency and lack of illumination are important to get good pictures of deep sky objects, and calmness of the atmosphere is not essential.
Consider astrophotography of deep-sky objects (DSOs), or deep sky objects. All DSOs have very low surface brightness, so the human eye, even with the largest telescope, sees them in black and white and does not see all the details of their structure. In contrast, film or camera sensor, when shooting with long exposures, can accumulate light falling on it for several minutes. At the same time, colors and small details that are invisible to the eye begin to appear in the picture. With the use of digital photographic equipment and the subsequent computer addition of a series of images, the total exposure time can reach tens and even hundreds of hours. In general, modern astrophotography is unthinkable without the use of computer processing of images.
But although image processing is a very interesting lesson with its own secrets and nuances, this is a separate very large topic and we will not touch on it in this article, especially since the source materials for processing still need to be obtained. Consider the astrophotography equipment requirements for astrophotography.
Which Mount Is Suitable for An Astrophotography Telescope?
For high-quality astrophotography, a good mount is almost more important than a telescope (lens) and a camera. So, a small telescope or even a photographic lens on a rigid mount will allow you to get excellent pictures, while even a 10 inch telescope without a good mount is completely useless for astrophotography. It is desirable that the mount has driven in both axes and the ability to control from a computer - this will allow using auto-guiding.
The fact is that even the toughest and most accurate mounts lead the telescope somewhat unevenly, during visual observations we do not just notice this. But during photography, tracking errors accumulate, and the stars in the image lose their round shape, become dashes or ticks. This becomes more pronounced the longer the focal length of the lens. The computer, using an auto-guide (a small telescope or a photographic lens with a camera, rigidly fixed to the main telescope tube), monitors guidance errors and adjusts the operation of the mount drives to eliminate them in time. In general, a smaller telescope on a more stable mount is preferable to a more aperture but unstable telescope.
What Is the Recommended Lens Aperture?
The telescope for effective astrophotography should be as fast as possible (have a relative aperture of f/6 – f/4) - this allows you to collect more light from celestial objects in a shorter period of time. Usually, for deep sky astrophotography, either a small semi-apochromat mounted on a mount with auto-guidance is used - as a compact travel tool if the volume of luggage is limited, or a reflector with an aperture of 200-250 mm on an equatorial mount.
It is highly desirable that the telescope has an electric focuser or at least a two-speed Crayford focuser - if during visual observations small focusing inaccuracies are compensated for by the lens of the eye, and we will not even notice them, then when using a telescope for astrophotography, this will lead to a blurred image.
Features of Shooting Deep Space Objects
Deep sky objects are usually taken in the direct focus of the telescope, while it is used as the lens of a DSLR. For this, a corresponding threaded T-ring is attached to the camera, which, in turn, is screwed onto the thread on the focuser of the telescope. The most popular among amateurs are Canon SLR cameras, but if you already have another camera, you can also use it.
For deep sky astrophotography, it is highly desirable to drive away from city lights - in conditions of strong illumination at exposures longer than 30 seconds, the brightness of the sky background increases too much, and it is impossible to get any high-quality images. An exception is shooting through narrow-band filters, but they cannot replace the dark suburban sky.
Features of Lunar-Planetary Shooting
Lunar-planetary photography has its own characteristics, and it often happens that an experienced deep sky photographer cannot even get a photo of the Moon through a telescope. The fact is that the moon and planets are very bright objects, and when shooting them, you do not need a long exposure. Usually they are filmed with webcams or special astronomical cameras, then the video is split into separate frames and folded using special software. There are special adapters for 1.25" diameter, with which the webcam is installed instead of the telescope eyepiece. Also, when shooting planets, black-and-white cameras are often used using light filters, respectively, of red, green and blue colors, and subsequent channel-by-channel addition to obtain a color image.
In lunar-planetary imaging, the requirements for the accuracy of telescope guidance are not so high, small errors are compensated for during processing. In principle, the first photos from a telescope can be obtained even with manual guidance, but it is still better to use a motorized mount. In order to increase the size of the planet's disk on the camera matrix, a telescope with the largest focal length is needed. To magnify it, 3x and even 5x Barlow lenses are used, while the equivalent focal length of the system can reach up to 10 meters.
Which Telescopes Are Suitable for Taking Pictures of The Moon?
A variety of telescopes are used for astrophotography of planets; the most common are Equatorial Reflectors. In this case, the larger the aperture, the more details and fine details will appear in the picture.
If you want to get your first photo through a telescope as soon as possible, you should try yourself in shooting the Moon - this is the most contrasting and rather simple object, and sometimes even a single frame is enough to get a high-quality picture.