New Barlow significantly reduces brightness

[Tosong]

Hi,

I recently bought a 3 element barlow from skies unlimited. I used it last night and was quite disappointed with the performance. The main thing was that it really reduced the brightness and made it hard to focus. I tried looking at Saturn and it wouldn't even focus. I'm almost at the limit of my scopes power (225 with a limit of 250) is this because it's a lousy barlow or is it because of my scope?

Cheers,

[Suzy]

Hi Daniel,

Very high magnification can darken an object. Saturn is a good example as you've found out.
Also, the quality of the "seeing" will determine how much magnification you can throw- the object will tend to shake and be hard to focus. All these things which you seem to be experiencing. :thumbsup:
On very few nights can magnification be pushed that high to the limits of the scope.

Here's a guide as to how much magnification you can push per inch of apperture.

http://www.seqas.org/

[Tosong]

That's a relief then :D thanks for the advice Suzy!