Quote:
Originally Posted by FredinBroome
By the way, a suggestion for a Baader barlow x2 I think it was was shown. Do you think this is necessary mate?
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A Barlow increases the focal length of a telescope by the multiplier value of the Barlow.
That means your 1200mm Dobsonian, with a 2x Barlow, then has an effective focal length of 2400mm.
That in turn increases the magnification of an eyepiece.
You need to know the maximum magnification your telescope can effectively use.
As an example, my 130/650 tabletop Dobsonian, has a theoretical max of 325x, but an effective max of 250x. This means that the maximum eyepiece I can use with a 2x Barlow is 5.2mm. Without a Barlow, 2.6mm.
My thoughts on a Barlow is that it is an essential piece of kit.