Quote:
Originally Posted by sil
Ok I'll show my dumbness here.
Barlow, teleconverter, Powermate are all the same thing right?
I assumed they were more a difference in product name (like Celestron, Meade, etc) or are they functionally different too (like Refractor, Reflector, SCT, etc)?
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Well, they serve the same purpose - they increase the folcal length of the telescope by certain factor.
In some telephoto lenses, you will find a last element (closest to the film.sensor) to be negative lens, single or doublet, sometimes called "field lens" (because it also flattens the field curvature of the front gooups of the optical system).