Amateur telescope
As amateur telescopes are telescopes which have in the field of amateur astronomy be used. They differ from the instruments used in observatories primarily in that they are used
- smaller size - the most common lens or mirror diameters are 10 to 30 cm
- cheaper and often transportable design
- easier control or manual operation.
Most common types
Mirror telescopes (reflectors) are predominantly in use because they are lighter and cheaper with the same light intensity. The most common types are the Newtonian telescope and Cassegrain telescope , the former also in the very simple Dobsonian mount .
Folk observatories and advanced amateurs sometimes also use special shapes such as Schiefspiegler , Brachyte or Maksutov telescopes , for which the mirrors themselves are sometimes ground . Small astrographs or Schmidt cameras are occasionally used for photographic purposes , or telescopes equipped with filters for observing the sun .
Reflector telescopes with an opening of about 20 cm (see eight-inch ) are particularly suitable for deep sky objects such as galaxies and nebulae , but also for observing comets and for astrophotography . They are also easily transportable on a suitable tripod . However, they are less powerful when it comes to high resolution .
So if you want to observe planets or double stars above all , opt for a lens telescope , also called a refractor. Such instruments cost around 2 to 3 times more than a reflector telescope with the same opening and weigh around twice as much, which requires a heavier mount . But they are much better in the resolution of fine details and have a slightly higher stability against nighttime temperature changes and with regard to optical adjustment .
Mounts
The most common are equatorial, parallactic mounts in which a coordinate axis is aligned with the celestial pole . This allows the telescope - the apparent rotation sky exactly - manually or electrically tracked and additionally with a fine movement to be adjusted manually. In the case of reflectors, the fork mount predominates , in the case of refractors the German mount . Both are also good for long-exposure sky photography, especially if a guide scope or a CCD sensor is available.
The inclined position of the axis (corresponding to the geographical latitude ) can, however, cause static problems if the telescope weighs more than about 20 kg. Then there is an increasing transition to azimuthal mounts whose axis of rotation is vertical and the tilt axis is horizontal. The disadvantage here is that tracking has to be carried out by both axes. Modern instruments usually have stepper motors with so-called go-to computer control. With long-term photography, however, the rotation of the image field must be taken into account.
Manufacturer and cost
In Europe known manufacturers of amateur telescopes are u. a. Celestron , Meade , Skywatcher , Tasco , Bresser , GSO , Lichtenknecker , Orion, and Zeiss (Oberkochen and Jena). Other companies produce optical components (auxiliary mirrors, eyepieces, etc.), astro cameras, servomotors or special mounts.
Entry-level models are available from around 80 to 100 euros. They are either lens telescopes with 6–8 cm opening or mirror telescopes with 7–10 cm with simple mounting on tripod, viewfinder and mostly 2 eyepieces. For 200 to 500 € you can get Newton or Dobson models with an aperture of up to 15 cm. For somewhat higher demands, many opt for an equatorially mounted eight-inch reflector (20 cm), for which 1000 to 2000 € have to be spent depending on the equipment (e.g. GoTo control). A long focal length refractor with a 10-15 cm aperture, suitable for planetary observation, costs similar. For additional eyepieces or good filters you have to calculate around 50 to 200 € each.
Some manufacturers also offer larger instruments, with classic Cassegrain reflecting telescopes from 25-30 cm with GoTo control costing around € 3000-6000, while the more simply assembled Dobsonian Newton costs less than half. With a 30 cm telescope opening (12 inches), however, the limit for car transport has been reached and a fixed observation point is preferable.
Areas of application
Amateur telescopes are used in almost the entire field of visual astronomy - with the exception of only the most distant deep sky objects (most distant galaxies, quasars). Even very faint nebulae can still be photographed, which can hardly be observed with the eye. The increasing light pollution , which affects many amateur astronomers living in the vicinity of cities, can in some cases be countered with special filters ( UHC , OIII ).
The most popular areas of application are:
especially in the solar system
- the moon , which is the ideal object for beginners to gain experience for observation and handling
- the sunspots , for which an inexpensive filter film is sufficient
- the bright planets , on which details are visible from about 50x magnification
- the varied dance of the moons of Jupiter
- Asteroids and comets
in our galaxy
- Double stars and variable stars
- Open and spherical star clusters
- Gas fog and dark fog
- Planetary nebulae and supernova remnants
- as well as methods of astrometry and spectroscopy
on deep sky objects
- Galaxies of various shapes and sizes
- Galaxy clusters
- various methods of astrophotography .
literature
- Ronald Stoyan : Telescope driver's license in 4 steps - Instructions for telescope owners . Oculum-Verlag, 2012
- Detlev Block: Astronomy as a hobby . Bassermann, Munich-Tetschin 2005