Barlow help please!

[matteboy]

Hi Peeps

Planning on getting a 2 x barlow to go with my new toy (200P) :D to double the mag with my current EPs

I've been looking at the Televue for around the £70.00 mark

Has anyone got any better choices, I've read that the Celestron Ultima is a good choice also Tal options are cheaper but I assume that with this kind of gear you get what you pay for?

Any advice muchly appreciated

[John]

You do get what you pay for although the TAL is no slouch.

I found the Tele Vue 2x and the Celestron Ultima 2x to be pretty much on a par (excellent). The Orion (USA) Shorty Plus (not the Shorty) is the same thing as the Ultima although often cheaper for some reason. Some don't like the "shorty" format in newtonians - something to do with the steeper light cone they use I believe.

A step up again from the above IMHO are the Tele View Powermates - the 2.5x one in the 1.25" fitting is a wonderful device - you just don't know it's in there apart from the power boost. But more £'s again of course

[matteboy]

Thanks John, I did have a look at the powermate, but £70 is going to be about the limit! I'm hoping to go for Televue EPs in the future, hmm green & black will look good in ya EP case!

[John]

Thanks John, I did have a look at the powermate, but £70 is going to be about the limit! I'm hoping to go for Televue EPs in the future, hmm green & black will look good in ya EP case!

You really can't go wrong with the TV 2x

And if you decide something else is more suitable in the future you will be able to sell it on with no trouble at all.

[johnkirkpatrick]

I use the orion shorty plus apo, its fantastic for the price £51@TH

Can't compare it to the TV though..

[sixela]

I fyou have the money for it, get the TV.

[russ]

I use the orion shorty plus apo, its fantastic for the price £51@TH

Can't compare it to the TV though..

Very little in it. If you end up with the TV, Ultima or Shorty Plus, you won't be disappointed. The Meade #140 Apo barlow also works very well and is not a shorty design.

[sixela]

Very little in it.

Except they're very different. The Celestron Ultima and siblings are very short, which makes some eyepiece designs more prone to vignetting, and also makes the magnification factor more variable depending on the eyepiece focal plane location (typically, they're not "2x" barlows, magnifying between 2.25 and 2.5x with most eyepieces).

And the baffling isn't completely as good either.

I do agree that for shorty barlows the Celestron Ultimas etc. are good, but unless you have a reason to get a shorty barlow (such reasons do exist, the TV 2x sticks quite far into the focuser or whatever else you stick eyepieces in --diagonals, Paracorr,...--) I prefer longer focal length two-element barlows.

And for those, if you want something better than a 2x TV you're ealready looking at a TMB 1.8x ED or Baader/Zeiss, both much more expensive.

[E621Keith]

Astroengineering's 4x imagemate looks like a good choice if you want high power

[pvaz]

For visual I would keep it in the 1.5x to 2x range. For 2 reasons:

1) Seeing conditions wont allow too much mag most of the time.

2) A barlow also messes with the EP eye relief. If you use a 30mm EP with 12mm eye relief with something like a 4x barlow, you may find yourself having to keep the eye over 40mm away from the EP (well outside the rubber guard) to get a view.

I had over 30mm ER when using a 31mm EP and a 2x barlow. The combination was quite useless, as I had to keep my eye far away but on axis with the EP not to see blackouts. To solve this problem, powermates ware invented, but that costs...