Brian,
When you say that there is dust in between the lens elements, how much? How bad? How large are the pieces of debris? Reason why I ask is that, in the case of any doublet, when you take it apart it is not easy to remove dust without getting more or "new" dust settling before you mate the two elements again. Blowing with a bulb atomizer will often not be sufficient to dislodge certain junk. In such cases a clean, dry red sable, reasonably large watercolor brush can work very well for a few contact swipes. I have done this with very good success, however, be prepared to take the top element off several times,,,trial and error, until you see no dust. Also, check the lenses against DARK background in order to see clearly that there is no dust, or, at least, that you have done a satisfacotory job, before securing lens in cell again. Now, I don't know how curved is the fluorite element in your scope, but I can tell you that the ED elements are extremely curved. This makes perfect mating extremely difficult. Achromatic doublets, especially longer focus ones, on the other hand, are actually rather easy to mate accurately. So, beware of the possible pitfalls, especially with an old Vixen 4" fluorite!
When you say that there is dust in between the lens elements, how much? How bad? How large are the pieces of debris? Reason why I ask is that, in the case of any doublet, when you take it apart it is not easy to remove dust without getting more or "new" dust settling before you mate the two elements again. Blowing with a bulb atomizer will often not be sufficient to dislodge certain junk. In such cases a clean, dry red sable, reasonably large watercolor brush can work very well for a few contact swipes. I have done this with very good success, however, be prepared to take the top element off several times,,,trial and error, until you see no dust. Also, check the lenses against DARK background in order to see clearly that there is no dust, or, at least, that you have done a satisfacotory job, before securing lens in cell again. Now, I don't know how curved is the fluorite element in your scope, but I can tell you that the ED elements are extremely curved. This makes perfect mating extremely difficult. Achromatic doublets, especially longer focus ones, on the other hand, are actually rather easy to mate accurately. So, beware of the possible pitfalls, especially with an old Vixen 4" fluorite!
