[bluesilver (Peter)]

Hi, I am just trying to find out some information in simple terms on how barlows have a visual effect on images through the eyepiece.

Say for example i have f5 Dobsonian.
If i use a 2X barlow it goes to a f10, a 5X barlow goes to a f25
Is this correct so far?

The question is, how dose this focal number effect the visual viewing through the eye piece compared to using the equivalent in a eye piece?
I mean if i were to use a 20mm eyepiece and a 2X balrow, what is the difference from using just a 10mm eyepiece?
Apart form the 10mm eyepiece will still be f5 where the 20mm and 2X barlow will be f10

Just trying to find out what the visual difference is through the eyepiece.
Will the higher the f number like f25 or f10 give more detail that it would at f5, I am also only talking about visual for the planets, not DSO.

I am guessing that also the lower the f number like f5 gives you more light, so f25 will be darker than f5.

I realise this a basic question all up, just having trouble trying to find any real answers.
As my theory was if the higher the f number like f25 gives you a darker image through the eye piece and can then give you more detail on the planets, would you be always better of using barlows to get the f number higher?

If anyone can help with this question in simple terms it would be most appreciated.
Thanks.