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Old 17-12-2018, 05:31 PM
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FredinBroome (Fred)
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FredinBroome is offline
 
Join Date: Dec 2018
Location: Broome WA
Posts: 74
Quote:
Originally Posted by JeniSkunk View Post
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.
I'll definitely keep a barlow in mind Jenifur for the future. I will see how my current rig goes and then play it by ear. I just purchased a second hand scope to add to my collection which I couldn't resist so funds are a bit tight for a little while hehe.


Thanks again for your help. Cheers Fred
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