EP size basics

[andyman]

Just finished reading the information on the link, very useful indeed, thank you.  Will definitely refer to this article when purchasing my EP's.  

One other question that arose from the link was the use of a Barlow to effectively double up a set of EP's, are they any particular drawbacks with this approach?  ie does introducing a Barlow into the chain cause reduced clarity?

If you are thinking of getting a barlow get a good quality one 

I use one and it doesnt decrease from the views at all

In some cicumstances it can enhance the views and also give more eye relief to tight eyepieces

[starwonder]

Thanks for the advice guys, I will buy a Barlow but feel suitably aware now of it's limits if pushed beyond reason, thanks.  I'll make sure it's a quality one too when the time comes.