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Altair Lightwave 3x Flat Field Tele Extender Barlow


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The 1.25“ Altair Lightwave 3x Flat Field Tele Extender Barlow weighs in at 195 grams and I make it 105mm tall. One of the reasons (if not the predominant one) I acquired this Barlow/amplifier was that its barrel is only 35mm leaving the remaining 70mm for the housing. This makes deployment in a 2“ diagonal (with an adapter) a lot safer as it helps ensure that the end of the unit doesn’t make contact with the mirror or prism surface. In my experience these sort of Barlows/amplifiers usually achieve focus in short tube refractors without the need for extension tubes.

 

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Altair give very little information on the specifications, although it probably has four elements as there are very similar looking four element ‘Extender Barlows’ on the market with a variety of brand names. It seems to have good coatings and features a compression ring, filter thread, a rubber grip on the internally flocked housing, and (unfortunately) a barrel undercut. The barrel itself appears to be chromed-brass and the entire unit has a quality feel to it. Although you’d probably expect that at a retail price of £85. The advantage of these ‘telecentric’ designs is that they don’t increase eye relief in use, unlike conventional Barlow lenses.

 

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I got first light with the Lightwave on the 14th of April observing a rapidly setting crescent Moon. I was using a modified ST80 and a Celestron Zoom inserted into an Amici prism. Stacked Baader Fringe Killer and Neodymium filters were threaded into the diagonal nose. The ST80 is my lightest grab and go set-up and the ‘Omegon’ Amici was a last second decision because I could actually see the Moon. I initially assumed it would be too low. The first thing that struck me was how sharp and defined the image was. I could detect no vignetting and considering how small the lunar phase was there was a wealth of detail.

 

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As the Moon got lower I switched the entire ensemble to a 2“ dielectric, discarded the Fringe Killer/Neodymium, and proceeded to observe several double stars. The seeing was a bit better than previous nights and splitting Epsilon and Delta Boötes at 100x were the first targets. I found I could easily push to 150x with ε Boo and the small green binary companion could be distinctly and clearly observed nestling in the first diffraction ring.

 

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Wikipedia claims that you can’t split this binary with anything less than a 76mm (3”) aperture. I do it fairly regularly with a 60mm ED doublet so I’m not so sure about that. Either way the ST80 plus zoom and Flat Field Tele Extender achieved it relatively easily. I tried a few small open clusters like NGC 1502 (Jolly Roger) and the M3 globular cluster at magnifications ranging between 50x and around 100x. I saw no aberrations in the field, apart from those attributable to an inexpensive achromatic doublet like the ST80. So; is it worth 85 quid? Well, it’s less than half the price of a Tele Vue Powermate and as far as I can tell has comparable performance.

 

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Edited by Nightspore
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