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........., and two come along at the same time! Arrived back home after been away for work all week to find that finally my new Televue 2.5 x Power Mate had at last arrived (ordered way back in early August from Orion Optics), along with a second hand Altair Astro 3x Barlow I bought off a member on here (thanks Paul! ) . So now I just need some clear skies to test both these new additions to my Astro kit out. Not looking good for tonight over here, but hoping at some point over the weekend, or at worst early part of next week to give them some first light. Be interesting to note any real difference between the two barlows, other than the magnification of course, with the Televue costing considerably times more than the Altair Astro 3 x Barlow!
Back in this thread I was looking for a planetary EP, dismissing barlows on the grounds of an unrequired increase in eye relief and the faffing around involved. The forum faithful persuaded me otherwise and the imminent relase of the ES Focal Extenders at a price well below one of their EPs, had me flexing the plastic. The main reason I folded, was because these are not barlows. They are, like the Meade Tele-Extenders with which they share a common heritage, what is often refered to as a Televue Powermate clone. I'm not actually sure that the concept is actually a Televue innovation, but as TV have been selling more of them, for longer than anyone else, lets run with the assumption that it is theirs. The important bit, is that unlike a barlow, which extends eye relief, a Powermate/Focal Extender doesn't. Instead of there being two (sometimes three) elements in one group that create diverging light rays to achieve their magnification, the focal extender employs a second group of lens elements to turn the magnified diverging rays, back to parallel. This prevents the increase in eye relief. The disadvantages are three fold. For starters, four elements are never going to be as cheap as two. Focal Extender prices start roughly where mid to higher price barlows leave off. Second, with a barlow, you can normally unscrew the lens element holder from the barlow body, which is handy. If you screw these elements directly onto the front of the eyepiece, you get a 1.3-1.6x increase in magnification instead. Indeed a less mentioned effect is that if you screw in an extension between the barlow body and the element holder, you can get a greater magnification than the native 2x (or whatever) of the barlow. You can screw it into the nose piece of your camera adaptor to provide a magnification increase for DSLR imaging etc. Barlows are quite versatile. A Focal Extender's magnification is fixed by the relationship between the two lens element groups. Even if they unscrew, the fact that the light rays emerge in parallel (telecentric) from the second group, means that even if they were a foot further away, they would still only provide a 2x magnification. Finally, a Focal Extender moves the focus point inward by it's own focal length*, which may be an issue for scopes with limited inward focuser travel. This issue, I have only seen mentioned a couple of times, so it presumably a non-issue under most circumstances, as reported by most users. I'd love to add my own experience to the pot, but my ES Focal Extender arrived whilst I stood under crystal clear, Alpine mountain top skies with nought for company but skis, the cloud being anchored at home where the Focal Extender had arrived. T'was always thus. My point is that Focal Extenders are not necessarily superior to Barlows. If you're into a bit of planetary webcam imaging, or a glasses wearer suffering from tight eye relief EPs, then a barlow may well be a better choice than the addition of a shorter focal length EP. If, like me, you are purely visual and are looking to add some planetary flexibility to some UWA EPs with ample eye relief, then the Focal Extender is a better choice. I see a lot of 'buy 'x', you can't go wrong' type statements, but I personally think there's a bit more latitude in individual requirements, than statements like that allow. The ES 1.25" 2x Focal Extender cost $79 plus $15 shipping from the USA. Import duty added £31.31, making a grand total of about £87 delivered. I say about, because the vagries of exchange rates, plus Paypal taking it's foreign currency exchange cut fuzzies the total slightly, but it's definitely south of £90. That is about half the price of a 1.25" 2.5x Televue Powermate, but only about a tenner less than a UK sourced TV 1.25" 2x Barlow. The value of this deal is therefore very dependent on your requirements, as mentioned above. As also mentioned above, I've only been back in the country a couple of cloudy nights, so I'll add my viewing impressions later. In the mean time, here's some piccies coupled with first impressions of the product: The ES packaging has changed, Whereas the ES 82s arrived in a plain black box with an ample expanded foam, clamshell inner, the Focal Extender has cranked it up a notch. The hefty foam remains, but the box is much thicker card, that by nature of it's wrap around magnetic fixing, is also now a double thickness. Gone is the plain black, all surfaces now resplendent in artwork by Will Tirion, the base of the box carrying a history of his work. A nice touch to add to seriously improved packaging. I would also note that, the box is only a shade smaller than that which carried the hand grenade weight and portions of my ES82 30mm EP which is a LOT bigger. If the Focal Extender arrives damaged, it won't be the fault of the packaging. On the subject of weight, the Focal Extender, in common with the ES82s, feels pretty dense in the palm. The combined weight of it, plus the 11mm ES82 tips the scales at a not inconsiderable 520g. Half that of the 30mm ES82, but double that of the 11mm alone and so worthy of note to Dob users in particular. Come to think of it, the weight, combined with the leverage of the complete assembly may challenge lighter EQ mounts. Here's a piccie of the pairing relative to a Skywatcher 20mm Super Plossl, which barely registers on the same scales! Artificial light and the resulting image tweaking in GIMP, has rendered the sheen of the element coatings invisible. Close inspection through a Canon 50mm f1.8 as magnifier, shows the coatings to be entirely even and resolutely green in hue. If inspection in daylight shows otherwise, I'll add it to my first light report. Likewise, with only LED spots and hammer-head flash, it's hard to show the element groupings, but other details are clear. The lack of blackening to the filter thread is disappointing, in line with all of the ES EPs I have. Liberal application of a black marker will be required to amelioate reflections, although the acid test will be actual use. Hopefully Jupiter will still be around when the cloud clears... To complete this phase of the review, I see from my original thread that I pre-ordered the Focal Extender on the 21st of December in a pre-Christmas fit of fiscal bravado. It shipped, almost a month to the day, on the 22nd of January. Notification of the 'comandgeddit' from the PO sorting office, was recived on the 4th of February, which is within the 10 working days norm. What I find interesting is that the Focal Extenders finally appeard on the ES website, well after I had ordered mine. The example on their website is number 28. Talk about mine being hot off the press..... TBC. Russell *I stand to be corrected on this one and indeed any other points!
I have up for sale my mint condition Tele Vue 2.5x Power mate 1.25". Bought only 4 months ago new. Original box in mint condition and rarely used. Looking for £140 which includes next day special delivery. Payment by PayPal (friends and family no charge, but if paying via services please add on 3.5% fees), or direct bank transfer. Gus <**now sold**>