Telrad viewfinder extremely convenient for Newton-Dobson telescopes manual pointing ...
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The Telrad is a researcher referred not right magnifying impressive ease and precision. The principle is simple and consists in reflecting on a tilted glass 45 ° target with 3 circles of different diameters. Looking behind the Telrad, towards the sky, the observer sees projection target superimposed on the sky. With a magnifying factor of time and the absence of lenses instead of a traditional researcher, Telrad shows no image inversion.
Through the target the sky appears to the naked eye. It is very easy to navigate and to find a low or bright object, simply superimpose the luminous circles on the desired area of the sky. After adjustment and calibration of sight first on a lamppost, then the moon and finally a star it is easy with a map pointing any object in seconds.
When the Telrad is perfectly aligned with the optical tube, the movement of the instrument according to the position of the target is particularly simple. For items that the observer knows the position simply center the star on the smallest target. The first is 4 ° field, the second 2 and the smallest 0.5 °. When this score is achieved, the object is directly in the field of ocular intermediate focal length.
For objects claiming the consultation celestial maps like Sky Atlas 2000.0 or Uranometria, simply draw a target of template Telrad can identify the distance from the object sought and a bright star nearby. If a nebula example is 10 ° to a reference star simply moving the instrument of twice the apparent distance of 4 ° circle and once one of 2 °. In seconds, even for objects invisible to the naked eye or drowned in the light pollution point your telescope effectively.
The installation of Telrad is very easy, it breaks down into two parts. The first is the mounting bracket immovably where Telrad lodge at each observation. Rounded to resume the shape of 150mm telescopes and beyond (Cassegrain, Newton, Dobson) it has two strips which stick to the optical tube. If the user has several instruments it is possible to order more while keeping a single viewfinder. The adaptation of the viewfinder is effected by two plastic screws on the dovetail. The Telrad Removable and fixed very quickly.
For calibration, and three cross trees tirantes screws mounted on spring are placed on the rear part. By varying the orientation of an internal reflecting mirror it is possible to finely adjust your Telrad and obtain a perfect alignment between the center of the smallest target instrument. Importantly, the intensity of the target varies. Depending on the star (planet, moon, nebula, galaxy clusters ...) turn the dial to the right of Telrad in contact with a potentiometer. An "Off" is available to prevent battery depletion. On the practical side, the target is visible that the observer is located a few centimeters of it or to several meters. This is an important point for Dobson glasses and possessors of carrying very large diameter. In the latter case, the Telrad can be positioned near the eyepiece, the observer will perform a first pointing at the foot of its instrument (Type 500-600 telescope or 800mm) and then refine to the top of the stool. Even a very large telescope is rotating very quickly to any deep sky object. Power is supplied by two LR6 batteries (not included) housed in the front portion of Telrad.
The assembly is delivered in a cardboard box filled foam precut ideal for storage after uninstalling the material. The Telrad is the ideal choice for those who want to point quickly and effectively his instrument. This is the choice for years to many seasoned enthusiasts attracted by the sight without magnification with a target. For the beginner guide his instrument without a tedious time to understand the inversion of the image of a classical scholar is very enjoyable and comfortable. Removable the Telrad is proposed in view of its compatibility on many instruments at a very attractive price.