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Sky and Telescope


Date: 8-17-2001
Price: £185 - approx $225
Design: Multi-coated zoom eyepiece
Description: Zoom eyepiece from TeleVue.


I have managed to get in several nights testing my new Televue 8-24mm zoom; enough at least for a fairly good stab at a review. The weather has been warm and dry with mostly clear skies, though there has been a little broken cloud and occasionally some hints of mist forming later at night. The telescope used was a Helios 150 F8 refractor which is largely unmodified except for the tripod which has been replaced with a wooden one. The MV1 filter supplied by Sirius Optics, but now available in the U.K. was in place for the whole evening, attached to the base of the eyepiece. I live in a fairly rural location (South Norfolk) with considerably less light pollution than in most parts of the U.K. As far as I able to judge seeing has been fairly good. Iíve been interested in astronomy for a number of years, but have only had a decent telescope for about 8 months.

Up until now my experience with eyepieces has been fairly limited. I have several Vixen Lanthanums, which I bought at the same time as the scope about 7 months ago. I have used Kellners, but these were with a different and far less capable scope so it wouldn't be fair to compare. I've been fairly satisfied with the Vixens. I like the eye relief even though I tend not to wear my glasses with the scope and, having had nothing to compare them against, have been generally pleased with their performance. There is a BUT however and that is that I have never been able to get a clear and focussed image using anything 10mm or below using a Barlow, either before or after the diagonal, limiting my useable magnification to about 140x (25mm with the Barlow before the diagonal). I put this down to seeing, but reading about other peopleís experiences I had started to wonder if my scope was defective in some way. I'm no expert by any means, but had carried out all the basic checks on the scope without throwing up any obvious problems. All the Lanthanums worked fine at the lower powers without the Barlow and the 25mm has been fine with. My 10mm has Barlowed fairly well with a friends Orion 200mm reflector.

Apologies for the lengthy preamble to what is supposed to be a review of the Televue zoom, but given what I'm going to say it's important to understand the context if the review is to be taken seriously. The zoom itself is a fine piece of engineering which has obviously been manufactured to a high quality. The multi coatings are superb and the zoom function works smoothly and easily. There are two models available; one with click stops at 24, 16 12 and 8mm and another with no stops. In the U.K. the one with stops costs about £10 more than the other. Which you have will be a matter of personal preference. I went for the model without stops as I couldn't see a need for them and paid £185 from Venturescope. The same eyepiece is sold under the Vixen and Meade names, the only differences as far as I can tell being cosmetic (and the price) 

I'd been desperate to try it out since it arrived and with the weather finally I left the scope out to cool. Given my experience to date with the scope my major hope for the zoom was that it would give me a stable image somewhere approaching 180-200x, 40-60x more than previously. When it finally got (almost!) dark the first object I looked at was the Moon. I used the zoom without the Barlow initially and with the stock diagonal which despite criticisms from others has always seemed pretty good to me, on the basis that the image was the same with or without the diagonal. The field of view at 24mm is a little narrow, around 40 degrees I think, but it didn't present a problem at any time during the night. The image was crisp, sharp and contrasty and snapped easily into focus through the whole range of the zoom (50-150X). It isn't quite parfocal and isn't advertised as such, but only needs a minimum of adjustment across the range. 

Very impressed by the initial view I popped the Barlow in before the diagonal to see how much it would take before the image broke down. I still don't know, because I puhed it right up to its limit (approximately 450x) and was still able to focus cleanly right across the range to the maximum. I was so amazed that I checked the set-up and my calculations several times before accepting what I was seeing, given that the accepted maximum for the scope should be about 300x, and then only in excellent seeing. It was like a completely new scope. I could have stayed with the Moon all night, but moved on to Mars, broadly speaking with the same result. Where previously I had a boiling multi- coloured ball at 240x with the 10mm Lanthanum I was able to get a fairly tightly focussed image at magnifications exceeding 300x and almost up to the maximum again during moments of good seeing. Of course there were no features to make absolutely certain because of the recent dust storm, but when I popped the Vixen 10mm in to check there was simply no comparison. The double double in Lyra was next. The Vixen 25mm had split this reasonably well at 140x or thereabouts, but the split with the Televue at 150x (both with and without the Barlow) was clearly better. The stars were more tightly defined pinpoints and the gap between them was distinctly darker. Just for fun I puhed the power right up again to 450x and where I had previously had two small pinpoints with a hint of a gap, I had two pairs of small round and still relatively bright balls with a clear and wonderfully defined gap. It was undoubtedly an optical illusion, but each star looked like a 3 dimensional ball; probably because I suspect that I was I slightly out of focus as I could see a couple of concentric rings around each star, much like an Airy disk. The stock focusser on the Helios scope struggles a bit with fine adjustment at this power, though in fairness the scope shouldnít be able to take it. 

I could have stayed with the double double for hours, but had a quick look at M57 and M81/82 before packing up. The Moon was past first quarter so the skies were not completely dark. Even so the images up to 140/150x was significantly better than with the Vixens. One perhaps overlooked benefit of the eyepiece is that you can play around with the magnification to get the best possible match (particularly with contrast) for the object that you are viewing. I guess you could do this with an extensive eyepiece collection as well, but not with the convenience of the zoom and certainly not at the price! 

Itís difficult to come to an objective conclusion. I had fairly low expectations for the Televue zoom and yet it totally outperformed my Vixen LV eyepieces. Is the Televue zoom really this good or do Vixen LV eyepieces and Chines 150mm refractors not match? Iím not really experienced enough to say. What I can say is that for £185 Iíve got a whole eyepiece collection in one (though Iíll be looking for a low power wide field eyepiece to complement the zoom). I honestly canít see a need for anything else. 

Minus points? The low field of view at the lowest powers might bother some people, but that isnít where its strengths lie anyway. I didnít find it as much of a problem as Iíd expected and knew that I would need a low power wide field eyepiece as well. The eye relief isnít quite as good as the Vixen across the whole range, but doesnít drop below 15mm which is more than adequate. Some reviewers have mentioned softness at 10mm and below, but I didn't see this. 

As a quick addition to the review before I sent it off I invited a friend round last night to see what he thought. He is a considerably more experienced astronomer than I with an Orion U.K. 200mm reflector on a Vixen mount. He also has a fairly comprehensive collection of Vixen LV eyepieces. 
In summary, his conclusions using the zoom with my refractor mirrored mine. He was amazed at how well it performed across a whole range of objects and was astounded by the sort of magnifications we were able to get from the refractor. We tried a number of Lanthanum eyepieces in the refractor, but couldnít get anything above 200x to focus with or without the Barlow, whilst the zoom was focussing cleanly at double this. He also noticed much less false colour than with the Lanthanums. I canít say I had noticed this, but to be honest I havenít had huge problems with false colour anyway, especially since buying the MV1 filter. It exists and it might bother some people, but the other benefits of the refractor completely outweigh it, in my opinion.

For the sake of fairness I should add that we were both slightly less impressed with the zoom in the Orion reflector. That isnít to say that it wasnít any good; it was certainly on a par with the Vixens across most of the range of magnification, except perhaps for the very top of the scale. There images did seem to soften slightly, though personally I find reflector images softer anyway. There also seemed to be the occasional internal reflection as well, though Iíve seen that with the Lanthanums with the reflector as well.

Bottom line? Incredible value for money and highly recommended. Particularly suitable for someone relatively new to the hobby who wants to view a wide range of objects without paying silly prices for premium eyepieces. Bear in mind that this eyepiece is only £50 or so more than a single 25mm Vixen Lanthanum, and over £100 less than a single TV Radian. Even with mid range Plossls you would probably be only to get about three for the price of the zoom. As with any accessory try one out before you buy if you can. (I bought from Venturescope because of their 14-day unconditional money back guarantee) Itís a very personal decision, but I canít imagine many people being disappointed if they are all as good as mine. My friend ordered his yesterday. He is also trying to work out how to hint to his wife that a 150mm refractor would make an ideal Christmas present!

Submitted by Chris East - chris.east@educ.suffolkcc.gov.uk - UK

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