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Which Barlow?

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Ok, I know this is probably just as tedious for the experts who get the questions about which scope or which EP.

It's not so much the brand, though that would be very useful- it's more the mag factor.

I am working on the naieve expectation that I would get my first scope and plug in my first EP and something like Saturn would appear in all it natural (magazine like) beauty.

Ok, maybe not but if I was to work on the basis of owning something like a 12" SkyWatcher dob with the stock EP's which mag barlow would you go for (if any?) which would give me a definite "Saturn" image.

Actually it's not my expectation - it's more my wifes when I show her my setup for the first time!

I think you know where I am coming from....


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The useful magnification is limited by the typical seeing conditions we have. Typically 200-250x is about the most that is useful, very occasionally a bit more.

Assuming a 12" F/5 scope with a focal length of 1500mm a 2x barlow lens with the supplied 10mm eyepiece will deliver 300x which is probably too much.

You might be better off buying a 6mm eyepiece and using that to give you 250x.

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Also it's worth remembering that 250x is still pretty small in the eyepiece. If you use too much magnification, trying to make the image bigger, you loose the detail. To me it feels like it won't come to focus.

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