A telescope equipped with a camera and designed to photograph astronomical objects is called an astrograph. Thanks to the industrial production of these devices, which began not so long ago, astrography has become available even to amateurs. Photographing distant terrestrial objects through a telescope is also of known interest.
Modern astrograph can be bought
In the telescope market, it is now easy to find a model suitable for photography, equipped with an equatorial mount with a mechanism for precise aiming and diurnal rotation. Some telescopes are already equipped with photo and video cameras that are compatible with a computer via a USB interface. In such cases, the device is accompanied by the appropriate software, which allows you to save the received photographs of celestial bodies. Prices for telescopes already equipped with cameras range from 15 thousand rubles. and more. Cameras specially designed for installation on telescopes can also be found on sale separately. Under certain conditions, these devices can be used to survey remote ground objects.
Installing the camera on the telescope
Any photographic lens with a focal length of 500 mm or more can be considered a telescope. Conversely, any telescope can be considered a telephoto lens if the photograph is taken without eyepiece magnification. Take a film SLR camera, remove the lens from it. Remove the eyepiece from the telescope. Fix the camera firmly on the telescope body so that the optical axes of both instruments coincide. You can use attachment rings or fix the camera with a standard screw or clamps. In the latter case, it is necessary to provide light isolation of the connection, which you can successfully do using black photo paper or a fabric opaque cuff. Focus the resulting optical system at infinity, for example, on the moon. Such an astrograph is suitable for photographing extended objects, for example, the moon, nebulae, comets and star clusters, and only taking into account the subsequent enlargement of the image.
Taking pictures with eyepiece magnification
The ocular magnification method is used to photograph planets. At the same time, the construction of a home-made astrograph remains the same, but a macro lens is installed on the camera, for which you can use, for example, a lens from an enlarger. Naturally, the focusing of the optical system will have to be done again. This method also allows the use of digital cameras, and even simple "soap dishes". True, it is imperative that the camera has the ability to completely wean off the automation, since the shooting will have to be carried out in manual mode. In this case, the eyepiece of the telescope is not removed. The sensitivity of the film or the camera matrix must be selected at least 200 ISO, and the lens aperture is fully open. The camera focuses at infinity, no zoom is applied.
The mount of the astrograph should be as rigid and vibration-free as possible. Equipping the mount with a diurnal rotation mechanism is mandatory when shooting faint objects, such as nebulae, since the exposure in these cases will be from one to several minutes, and the Earth, as you know, rotates.
Some details to know
Never take pictures of the Sun and do not point a telescope or astrograph at it without special filters, this can guarantee the destruction of the camera and blind the observer. For astronomical photography, you must choose a clear, windless night, and if you are not photographing the Moon, then a moonless night. It is better not to take photographs of objects located above the horizon without special need - the quality will be reduced due to large thermal and atmospheric distortions.When photographing comets, the mechanism of the daily movement of the mount does not help because of the comet's own motion, and you have to manually move the telescope using standard microscrews and a guide, that is, a small telescope rigidly mounted on the telescope.