Quote:
Originally Posted by doppler
A long barlow will fit in most newtonians but the barrel is too long to fit in a diagonal or in my case the focusser of my mak cassegrain even without the diagonal. If you put it in before the diagonal the eyepiece might not come to focus. Barlows are designed to have an eyepiece (or camera) fitted directly to the top.
ps my diagonal is threaded so the 2 filter idea would work on my diagonal
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Some of these Barlow types have tradeoffs.
Shorties...their compact and easier to manage, but may cause vignetting in longer focal length say 32mm eyepieces , and even add some astigmatism in the periphery and other problems with such a rapidly changed lightpath...a reason I gave up on the cheapy shorties years ago.
The longer ones ..not so many problems.
A good TV barlow for example was designed to be used with their EPs , and mixing brands can lead to undesirable outcomes...thats my experience.
bigjoe.