Quote:
Originally Posted by Constant
Quite quickly I have become obsessively fearful about anything that links the action "cleaning" and telescope "objective" to the point I toss and turn in my sleep from memories of well intentioned yet misdirection swipes at objectives with cleaning tissues.
My reading indicates there is proportionately less fear in raising a cleaning cloth to an eyepiece than there is raising a cleaning cloth to an objective and that many premium eyepieces are formed from Lanthanum Glass
Why then when many good eyepieces are formed from Lanthanum Glass and that those La eyepieces generally tolerate quite harsh treatment and rigorous cleaning why not simply form objectives from La? allowing for misdirected and over enthusiastic cleaning. Is it a cost thing that prevents the use of La as an objective? Is it technically difficult to grind a large piece of La Glass?
Or..... is my belief that La eyepieces tolerate cleaning totally wrong?
Befuddled Cleaner...
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The different refractive indices, suit different optical designs.
Lanthanum glass has a very high refractive index about 1.7, fluorite and other ED glasses & optical glasses are much closer to 1.5. The high refractive index is probably better suited to eyepiece design, the ED glasses to objective design.