----------------------------------- Mircea Pteancu 27 Mar 2011 19:00 ----------------------------------- Nu doresc sa dublez un subiect care a inceput sa fie dezbatut foarte bine la topicul ''Ce am vazut aseara''.Si spun acest lucru deoarece vedem acolo cum un grup relativ numeros de amatori, folosind o gama apreciabila de instrumente, fac observatii al caror scop este detectarea diviziunii Cassini. Nu stiu daca acest lucru are importanta si pentru altii,dar gasesc acest lucru de-a dreptul incantator.Acest lucru m-a motivat sa ma inscriu pe forum,sa fac parte dintr-un grup de observatori care fac observatii si experimente pe care si le impartasesc spre folosul tuturor si cu care sa ma pot intelege ,simplu si usor in limba materna. Citez din ''Through the Telescope'' de James Baikie,London,1906,capitolul XI,''Saturn'',pag. 182: ''...Webb states that when the ring system was at its greatest breadth he has seen it with a power of about twenty on only 1 1/3-inch aperture. A beginner cannot expect to do so much with such small means ; but at all events a 2 -inch telescope with powers of from 50 to 100 will reveal the main outlines of the ring very well indeed, and, with careful attention will show the shadow of the ring upon the ball, and that of the ball upon the ring. When we come to the question of the division in the ring, we are on somewhat more doubtful ground. Proctor affirms that '' the division in the ring (Cassini's) can be seen in a good 2-inch aperture in favourable weather.'' One would have felt inclined to say that the weather would require to be very favourable indeed, were it not that Proctor's statement is corroborated by Denning, who remarks that '' With a 2-inch refractor, power about ninety, not only are the rings splendidly visible, but Cassini's division is readily glimpsed, as well as the narrow dark belt on the body of the planet.'' The student may, however, be warned against expecting that such statements will apply to his own individual efforts. There are comparatively few observers whose eyes have had such systematic training as to qualify them for work like this, and those who begin by expecting to see all that skilled observers see with an instrument of the same power are only laying up for themselves stores of disappointment. Mr. Mee's frank confession may be commended to the notice of those who hope to see at the first glance all that old students have learned to see by years of hard work. '' The first time I saw Saturn through a large telescope, a fine 12-inch reflector, I confess I could not see the division (Cassini's), though the view of the planet was one of exquisite beauty and long to be remembered, and notwithstanding the fact that the much fainter division of Encke was at the moment visible to the owner of the instrument!'' It is extremely unlikely that the beginner will see the division with anything much less than 3 inches, and even with that aperture he will not see it until the rings are well opened.'' Precizari,in caz cazul unor probleme cu limba engleza: -Webb afirma ca a vazut clar ansamblul inelelor lui Saturn cu o marire de 20x intr-o luneta de 33 mm.Nu si diviziunea Cassini. -in schimb Proctor si Denning au vazut clar diviziunea in lunete de 50mm -autorul Baikie atrage insa atentia asupra importantei antrenamentului,al ''ochiului format'' cum zicem noi,sublinierea imi apartine -este important sa fim onesti cu noi insine pentru a intelege unde suntem situati ca nivel de experienta ,pentru a sti ce abilitati trebuie sa ne dezvoltam. Pentru aceasta Baikie citeaza confesiunea lui Mee care nu a vazut diviziunea Cassini printr-un bun reflector de 12 inch prin care proprietarul vedea chiar si diviziunea mult mai slaba a lui Encke. Mircea