Premium Barlow help please

[Kai]

I am in a quandry with respect to my eyepieces

I have a 12 inch Flextube and to complement it 3 Pentax eyepieces , a 10mm Xw / 14mm Xw and a 32mm Xl. Now these 3 serve me rerally well as you would expect on the majority of targets but i am lacking a bit with Planetery / Lunar.

In an ideal world i would get a 5 and 7mm Xw but i really cant afford that sort of outlay so my question is would i loose much by adding a 2x Televue barlow to my existing eyepieces ?

Any advise would be helpfull

[russ]

A good quality barlow, like the TV 2x, would be a good investment and turn your 10mm and 14mm Pentax eyepieces into decent planetary performers with the Flextube. It would give you two good planetary powers (214x and 300x) in one shot, while retaining the good eyerelief and excellent AFOV of the XW's. In essence giving you another 5mm and 7mm XW but saving you hundreds.

Russ

[brianb]

In my experience the Celestron Ultima SV 2x outperforms the TV 2x barlow ... the TV Powermates are equal to the Ultima for visual, better for imaging but at a significantly higher price level. And there's nothing cheaper than the Ultima / TV barlow that has a performance which is close - not even the Tal, which some people rave about. (Excellent value but not as good optically!)

[MikeP]

Hi there Kai,

As you know, I have the same scope and the same eyepieces. I've also got a 2.5x Powermate but I've not tried combining them.

Next clear night, I'll give it a go. I know its not a Barlow but it should give some sort of indication.

Mike

[John]

I had a 2.5x Powermate and a Celestron Ultima a while ago. I agree that optically there is little to pick between them but I found that the Powermate had other advantages such as retaining the same focus point, not expanding the eye relief as barlows do and a compression ring fitting so I kept that one.

In terms of image quality, I gained little or nothing by moving to just eyepieces (ie: no barlow / Powermate) other than not having to fiddle around with another bit of kit in the dark.

I'm shortly to take delivery of a Meade 2" 2x Tele Xtender and I'll be interested to see how that does.

[Rob]

In my experience the Celestron Ultima SV 2x outperforms the TV 2x barlow ... the TV Powermates are equal to the Ultima for visual, better for imaging but at a significantly higher price level. And there's nothing cheaper than the Ultima / TV barlow that has a performance which is close - not even the Tal, which some people rave about. (Excellent value but not as good optically!)

I disagree here, the TV x2 is far better than the ultima. And to follow that up I would go for a Orion Shorty Plus ED x2 barlow from SCS astro.

Rob

[Kai]

Thanks for the input so far

Can somebody explain in simple terms the differences between a TV Barlow and a TV Powermate , ie is the powermate that much better than the barlow ?

[arad85]

The powermate has an extra set of lenses so the light rays that it emits are close to parallel rather than diverging with a barlow. This means you get a constant(ish) magnification rather than it changing with distance from the lens. Take a look at TeleVues pages - they explain it....

[riklaunim]

GSO makes cheap good APO or ED barlows. In UK they are usualy branded as Revelation

[russ]

In my experience the Celestron Ultima SV 2x outperforms the TV 2x barlow ... the TV Powermates are equal to the Ultima for visual, better for imaging but at a significantly higher price level. And there's nothing cheaper than the Ultima / TV barlow that has a performance which is close - not even the Tal, which some people rave about. (Excellent value but not as good optically!)

Sorry Brian but that's not quite true. There is a cheaper alternative to the Ultima and that's the optically identical Orion Shorty Plus 2x. Undercuts the Ultima by £17.

That aside, if i was looking for a barlow now (i have the Ultima btw) i would take the first well priced secondhand Ultima, Shorty Plus, TV 2x or Antares Elite (also an Ultima clone) that appeared. Anyone of those would be a good barlow to own. And at half the cost of the Powermate. Cost no option, go with the powermate but as the original poster highlighted cost as a consideration, that probably counts out the Powermate.

[Kai]

The powermate has an extra set of lenses so the light rays that it emits are close to parallel rather than diverging with a barlow. This means you get a constant(ish) magnification rather than it changing with distance from the lens. Take a look at TeleVues pages - they explain it....

Ahh okay , so is that much of an issue with parfocal eyepieces as presumably the focal point is the same ?

[John]

Ahh okay , so is that much of an issue with parfocal eyepieces as presumably the focal point is the same ?

When I was using a Powermate 2.5x with Nagler T6 eyepieces the focal point remained pretty much the same as the eyepieces on their own and they retained their parfocality (is that a real word ).

Whether that would be the same using non-Tele Vue eyepieces I don't know.

[johninderby]

Thanks for the input so far

Can somebody explain in simple terms the differences between a TV Barlow and a TV Powermate , ie is the powermate that much better than the barlow ?

I came across a quote recently from Al Nagler about the barlow and powermate. He said that with a Newtonian the powermate has no advantage or performance benefit over the barlow. He said the powermate was designed for use with a diagonal, and that's where it's additional set of lenses allows for better correction.

John

[Kai]

Just to complete this thread , i have ordered a 2x TV barlow from Telescope House today to qualify for their Astrofest 10% discount so it cost a shade under £72

Many thanks for everybodies input !