raffaele78 ha scritto:
E come si fa a collimare il diagonale?
effettivamente, mi correggo, bisognerebbe collimare prima il tel senza diagonale, e poi controllare se il diagonale è centrato correttamente .
un modo di fare ciò è descritto qui:
"The Diagonal:
Having a properly collimated scope makes it relatively simple to test the degree to which the diagonal is square-on. You center the collimating star in the scope. Remove the eyepiece and insert the diagonal. Reinsert the eyepiece and focus. If the star is not in the center of the field of view, this in itself is a sign that the diagonal is not square-on. Rotate the diagonal until the star is centered in it. (This may put your neck in an odd position.) If rotating the diagonal does not center the star, then using the declination and right ascension adjustments on your telescope mount, by using small adjustments, center the star in the center of the field of view.
Once the star is centered in the field of view. Rotate the diagonal 90 degrees. Look to see where the star is. If the star is still in the center of the field of view, then rotate the diagonal to the 180 degree position. Observe again. If the star is still centered, you are finished. Your telescope is collimated and your diagonal is square-on.
However, it is very likely that when you rotate the diagonal 90 and then 180 degrees, the collimating star will not remain in the center of the field of view. At this point you need to remove the diagonal and adjust the position of the mirror in the diagonal.
Diagonals come in many forms. Some have a plate on the back held in place by four screws. Some diagonals have a circular plate held in place by one tiny recessed screw. In the latter case you may need to purchase a specifically sized very small screw-driver to loosen that screw and remove the plate to get at the mirror. There are other designs as well. Once you loosen this plate, you will then either find a thin piece of front silvered (aluminized) glass lying on it or attached to it. Or you may find a thick elliptically shaped beveled mirror which slides into pre-cut slots. Regardless, you will need to take a tiny piece of paper; perhaps as small as 5 millimeters long, 1 millimeter wide and a half millimeter thick. You then position this piece of paper at one of the four sides of the mirror at an edge between the rear of the mirror and its backing, or at an edge between the surface of the mirror and its slot. You will now need to snugly reassemble the diagonal, reinstall it in the scope and retest the diagonal as described above. In all likelihood you will have to repeat this again to try a new position. Quite possibly, after only three or four tries you will find a very good; square-on, position. It is also possible that you will need to make the paper thinner or thicker. When you can turn the diagonal 90 and 180 degrees on a star centered in the field of view and it remains in the same position, you know your diagonal is square-on. "
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