INSTRUMENTS

ASTRAL TELESCOPE

BASIC NOTES

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The telescope is an optic instrument that, by means of mirrors or lenses, collects and focuses the light coming from far objects and presents their enlarged image to the eye of the observer. The telescope has two principal characteristics:
1) it can collect more light than the human eye can, and so facilitates the observation of dim lite or distant objects.
2) it reveals, with greater resolution power, the finest details, invisible to the naked eye. This power increases with the widening of the aperture (the diameter of the objective).
There are two principal categories of telescopes, according to the use which they are pure - convertible telescopes - astronomy telescopes

CONVERTIBLE TELESCOPES
Convertible telescopes are generally, light instruments. They are easily portable and convenient for carrying and intended mainly to facilitate daytime observation of terrestrial objects.
They can be used for bird watching, on walks, to follow sporting activities or for general nature observation. They are useful on all occasions when a simple binoculars is inadequate.
With this type of telescope astronomy observation is also possible (in particular observation of the moon or planets) when it is mounted on a stable tripod.
A particular advantage of this type of telescope is that by means of a simple adaptor it can be transformed into a powerful teleobjetive for a reflex camera. In this case it plays the part of an eyepiece. Connections for the most common brand of camera or photography accessories are available and this telescope has been in wide demand by many people who consider its plotting scope to be an essential part of their photography equipment.

ASTRONOMY TELESCOPES
From the optic point of view, this type of telescope resembles the other, while having distinctive characteristic of its own.
To begin with its optic quality (external work, quality of glass, mechanical centering of its component parts) has to be extremely accurate in order to satisfy requirements. When are used in observation of planets or to distinguish double stars, precision is a must. The mechanics of mounting is also of prime importance when observing stars, as they appear, or in celestial spheres caused by the rotation of their planet. A simple tripod is all that is necessary for observation at a low enlargement level. On a higher level, the movement of the celestial sphere requires something more. It is easy for objects to move outside the field of vision. Besides, the movement of the celestial bodies is not necessarily horizontal or vertical. It depends on a geometry which depends in turn on the point of observation. It is necessary to have suitable backup in order to observe. Instruments developed for this purpose are necessary to facilitate observations.

RESOLUTION POWER  

As we have already seen, the capacity of a telescope to separate objects positioned close to each other is called resolution power. This depends on the aperture power (diameter) of the objective according to empirical formula developed by Dawes as shown in the diagram.
The formula is theoretical as it is necessary to take into account the atmospheric turbulence which can notably influence the resolution power of a telescope.