Quote:
Originally Posted by Solanum
As a beginner I'd be interested to know why this is. I thought a diagonal just reflected the light 90 deg, why does it have an effect on magnification?
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Hi Everard.
It's because the diagonal is acting as an extension tube to the barlow. In almost all barlows, an extension tube will act as a multiplier. In some barlows (eg: 2.5x powermate), the extension tube actually decreases magnification.
Check out these 2 pages on the televue site for some nice graphs. Obviously it may not be the same for other brand barlows, but you get the idea.
http://www.televue.com/engine/page.asp?ID=41
http://www.televue.com/engine/page.asp?ID=42