2" Barlow

[Frank the Troll]

Is there much advantage using a 2" barlow with 1.25 lenses, and would it better suit a 2" diagonal?

[John]

A 2" barlow needs a 2" diagonal if it's to be used with a refractor, SCT or mak-cassegrain.

Some widefield 1.25" eyepieces can have their field of view vignetted by a 1.25" barlow so a 2" barlow would overcome that.

 

[Frank the Troll]

11 minutes ago, John said:

A 2" barlow needs a 2" diagonal if it's to be used with a refractor, SCT or mak-cassegrain.

 

 

I have both a frac and a newt, I could use iit on, with a few 1.25 widefield EP's

So a 2" diagonal would be worth a punt?

[Louis D]

You wouldn't need a diagonal to use it on your newt as long as it has a 2" capable focuser, so give it a go there.  The GSO 2" 2x is phenomenal.  Make sure it says Taiwan and has a shiny chrome barrel with a black optics section that unscrews from the bottom.  Look at the Agena Astro site for an image of it.  The FLO ED Deluxe appears to be the poorer Chinese made version, but I could be mistaken.

[Frank the Troll]

10 hours ago, Louis D said:

You wouldn't need a diagonal to use it on your newt as long as it has a 2" capable focuser, so give it a go there.  The GSO 2" 2x is phenomenal.  Make sure it says Taiwan and has a shiny chrome barrel with a black optics section that unscrews from the bottom. 

Mine is supposed to be an ED version, but no makers name, the optics does unscrews at the bottom.  Compression ring for 2" & 1.25 EP's

Yep the newt takes 2"

[John]

Those long barrelled barlows can cause some issues when used in a diagonal because you can't insert them all the way so the point of focus of the eyepiece alters quite a bit. Scopes with limited focus travel might not be able to bring them to focus.

Some newtonian focusers have a ridge down inside their drawtube that limits the length of barrel that can be inserted. It's worth checking that out as well.

I did own one of the GSO / Revelation 2" 2x ED barlows for a while but I can't recall much about it. I probably used it mostly for barlowed laser collimation rather than for viewing.

 

 

[Louis D]

He could always just unscrew the optics and screw them into the telescope end of his 2" diagonal if infocus is an issue.  It should come out close to the same distance (about 100mm give or take for most 2" mirror diagonals).  That one appears to be the Chinese clone that doesn't work as well as the Taiwanese one.  There was a recent discussion on Cloudy Nights about both.

[Louis D]

I found the CN discussion post about the 2" 2X variations here.  FLO's definitely looks like the newer Chinese Knight Owl 2" 2x barlow to avoid.  I'm not sure who sells the GSO version in the UK.  The 1.25" adapter is a totally different design.

[Ceramus]

I have the Revelation 2" Barlow and use it both for viewing and laser collimating a SW300p fexitube. I also unscrew the lens off the barrel and use the 2" compression ring with an adaptor for all my EPs. Much better than the the 2 screws barrel supplied with the scope, which has a bit of slop.

[Frank the Troll]

56 minutes ago, Ceramus said:

I also unscrew the lens off the barrel and use the 2" compression ring with an adaptor for all my EPs

I shall give that a go on the newt, cheers

Better get a 2" diag for the frac then

 

[Dave In Vermont]

I've been hearing good reviews of the GSO 2" Barlow over here in the US on forums for awhile. An example can be found here:

http://agenaastro.com/gso-2-2x-ed-barlow-lens.html

The price doesn't hurt either.

Dave