2" barlows

[kingcarp]

hi guys, i would like to buy a 2" barlow lens for my sw 100ed but my existing eyepices are the 1 1/4 sizes. i know they usually come with an adapter but was wondering if it effects the performance, thanks for any help

[hemihaggis]

you will still be looking through a 1.25 ep ... its pointless having a 2" barlow in that case ???

[AstroMum]

I have a 2" x2 barlow and no issues using my 1.25" EPs. It's not going to make the view through them any bigger though.

It's not a bad idea to buy a 2" barlow if you think you might use 2" EPs some day. Apart from the additional weight (and they are pretty chunky) there's no reason not to go for one as far as I can see.

Have a look at my thread here if you want to get an idea of how big the 2" barlow is compared to a 1.25" EP:

http://stargazerslounge.com/astro-lounge/175953-new-eps-skywire-have-arrived.html

My barlow was only £37, so didn't cost any more than a 1.25" equivalent.

[kingcarp]

thanks fr your responses, i will be buying some 2" lenses in the future, i just was not sure if using a smaller eyepiece in it would make a differnce optically, thanks

[John]

I guess there is an argument that it might make a difference optically. The figure of lenses, especially low cost ones, is generally more accurate in their central regions than their edges I believe. Therefore the "sweet spot" with a 2" diameter barlow could be larger, I guess

I've heard this argument used for 2" diagonals as well.

I'm happy to be pursuaded that this in not the case though