2inch Barlow - diagonal friendly

[Stargazer_00]

I am building a set of 1.25" and 2" 82 degree eyepieces and the weak part of my set is the barlow. Still using the thing that came with my scope, the Skywatcher generic 1.25inch barlow.

i did buy a 2inch ED Revelation Barlow but it has a very long barrel. I need kit that works in both my scopes. Both have 2 inch focusers, one is a normal reflector style crayford and the other is a refractor, so uses a 2 inch diagonal.

I need a good quality barlow with a short enough barrel to fully insert into a diagonal without fouling on the mirror. The diagonal is also going to be upgraded shortly, going to get one from FLO http://www.firstligh...r-diagonal.html

I heard good things about the Antares 1.6x 2inch barlow but cant see to find a UK retailer. i found one on ebay in the states, is this the fabled thing?

http://www.ebay.co.u...=item1c2cff542c

Are there any UK retailers who sell this barlow?

What other good options are there? 1.6x seems nice. I wouldnt want to go over 2x. Is it "shorty" barlows that Im after?

Id like something that works in both scopes. Have no issue with always keeping it at 2 inch and putting 1.25" into it with a built in reducer. I assume using a 1.25" eyepiece in a 2" barlow does not introduce any negative optical effects. Or do you actually need a 1.25" barlow for 1.25" eyepieces to get the best views?

For reference the EPs I am buying are Celestron Luminos. That range offers a 2.5x barlow only which i think is too strong

[John]

It's fine to use 1.25" eyepieces with a 2" barlow.

The Antares 1.6x is the best barlow I've used but I can't think of another that is a true "shorty" format. There are other shorty alternatives but they are things like the Tele Vue 2" 2x Powermate or the Bresser / Meade 2" 2x TeleXtender but the price has gone way up over the Antares with this sort of kit.

If you do get an Antares 1.6x be aware that they don't come with the 1.25" - 2" adapters but those can be bought separately.

There was an Antares for sale on E.Bay in the UK a few days back for around £65 I think.

[Stargazer_00]

i havent got the 2 inch diagonal yet to try the revelation ED barlow. Is that just a total waste even trying or does it work half in half out?

seems like a bit of a hole in the market finding barlows that go all the way into a diagonal.

[John]

The Revelation ED 2" 2x barlow does work even though it does not fully insert into a diagonal. The impact of this is that you need more inward focuser to bring an eyepiece to focus. Barlows cause a bit of this anyway and the bit thats sticking out just increases it. If you have plenty of inwards focuser travel left with the 2" diagonal in place and an eyepiece at focus then the Revelation 2" ED barlow will work. If you only have 10mm or so then you may not be able to get eyepieces to focus when using the barlow.

Sorry I can't be more precise and I agree that it's a bit frustrating with 2" barlows having, in the main, rather long barrels.

Maybe someone who has tried the exact combination that you are proposing will chip in.

[Stargazer_00]

Is it an option to screw the lens part of the ED barlow onto the part of the diagonal that goes inside the scope? I dont even know if they are threaded, just the lightpath between that part of the diagonal and the EP lense is probably close to the length of the barrel on the barlow.

[John]

Is it an option to screw the lens part of the ED barlow onto the part of the diagonal that goes inside the scope? I dont even know if they are threaded, just the lightpath between that part of the diagonal and the EP lense is probably close to the length of the barrel on the barlow.

Possibly, but I've not tried that personally. It would be worth checking the inside of the drawtube of your ST120 to see if it could accommodate the additional length that the barlow element would add to the diagonal barrel.

It's one of those things that you really want to try out before committing ideally - there could still be some issues with the focal plane being moved to a place where your can't achieve focus.

If you could find a used 2" ED barlow you could buy it, try it, then sell on with little / no loss if things don't work out.

[Stargazer_00]

Oh I own a 2" ED barlow already and use it on occasion in my Dob It'd be no trouble to try this out when a diagonal arrives. If it doesnt work I'll try source a antares from the US