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Sorry about my slip, I was forgetting it's not a linear progression. I plead
old age. Regarding your teleconverter; it doesn't matter how you increase magnification, barlow, teleconverter, or eyepiece projection, you will always have a dimmer image that will require longer subs. The three items do however have different purposes and properties. Cheaper barlows usually have only one or two lenses, and are designed only to magnify, usually 2 or 3 x .Teleconverters are designed to work with camera lenses that are generally well corrected, hence have usually either 4 or 7 elements designed to try and maintain that good correction. Eyepieces are another ball game altogether, each type introducing it's own specific qualities and optical aberrations. For simple 2x mag you're
better off using a barlow rather than EP projection for the above mentioned reasons. I have never tried using a teleconverter with a scope, but because it is trying to maintain the good correction of the image that
passes through it, it might possibly introduce aberrations of it's own.
I will be interested to see how you fare with it.
raymo
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