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Zhumell 1.25" 8-24mm Zoom Eyepiece
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I’ve been visually observing since the summer of 2008 from East TN. I spend more time observing DSOs (clusters & galaxies, mainly). I swap back and forth between telescope viewing and binocular viewing. In the quest to get a better eyepiece for a telescope that my parents purchased for me several years ago, I found a Zhumell 8-24mm zoom eyepiece for a really good price on a popular web auction site. I’ve had this eyepiece for over a year now, so it’s time for a small review of it.
My first impression was “wow” this is an awesome eyepiece. In truth, it was my first 1.25” eyepiece and I still have it, so that might say a little about how I feel about it. To add further, it is the one eyepiece that I always take out with me for use in all of my scopes regardless of what I’m going to look at.
I’ll first talk about the mechanics of it. It arrived in a heavy duty bolt case that has “MZT8-24” stamped on it. The finish is nice, the eyecup (always up, you can’t fold it down) is soft rubber, and there is a rubber grip on the side for adjusting the focal length. The zoom function is nice and smooth (not too easy turn, but not too hard to turn either). On very cold nights, it is only a little more difficult to turn, but not much. The eyepiece is not parfocal – I have to adjust focus by a small amount on all of my scopes when going from one end of the zoom range to the other.
This is not a click stop eyepiece – the labels on the side are 24mm, 18mm, 12mm & 8mm – there are no marks as to exactly where these occur, so accurately dialing in a particular focal length isn’t possible (I suppose you could measure with a flexible tape measure and place some marks where they occur), but this isn’t a concern for me. One last item of mention – the field stop is 18.3mm, measured at the very bottom of the eyepiece using the inside diameter of the metal ring that holds the bottom element in.
Picture of bottom:
For comparison’s sake, here are some pictures of most of my EP's (including the Zhumell zoom):
Side view, from left to
Astrola 32mm 2"
Rini 1.25” 52mm
Zhumell 1.25” 8-24mm zoom
Orion Sirius 1.25” 40mm
Zhumell 1.25” 32mm
Meade 1.25” 4000 series 26mm
Top views, same order as above:
Now, for the optics. The advertised specifications are: AFOV= 40° (at 24mm) to 60° (at 8 mm), ~20mm of eye relief, and multi-coated optics. The lenses are indeed nicely coated to a green color.
Crudely measured AFOV, using the crude formula AFOV=TFOV * Magnification yielded 33° at 24mm and 64° at 8mm; TFOV was calculated for this exercise using Starry Night Backyard 4.0.5 backyard and finding some stars that just fit into the FOV. Once again, this is a very crude measurement and calculation that is prone to over 20% error, so take this with a grain of salt. I haven’t noticed any annoying reflections or ghosting with this eyepiece, but they could be there as I don’t observe the brighter objects often.
I compared the Zhumell zoom to a Meade 4000 series 9.7mm super Plössl - daytime views are comparable; nighttime views are much better in the Zhumell, even at the 8mm setting. I tried both eyepieces out in my 4" refractor and my classic Sears 80mm refractor, both with the same results. The Meade gives slightly fuzzy views, but was capable of splitting Epsilon Lyrae at ~83x in the 4". The Zhumell can do the same thing at the same power, but with better eye relief and a sharper image (and better separation between components). Additionally, the Zhumell zoom beats any of the other eyepieces that I have barlowed into a focal length that is covered by the Zhumell.
With a 3x barlow in my 10” dob, the Zhumell zoom barlowed well at 24mm, but the 8mm setting can’t achieve focus on Jupiter (no surprise there, really, the power was ~463x!), arnd the Moon’s edges appeared OK but a little soft at 8mm. With a 2x Zhumell barlow, the full range of zoom barlows pretty well, but I don’t use the 8mm setting often due to the limits on seeing.
With the exception of a Circle K 0.965” 7.5-22.5mm zoom eyepiece, I would say that the Zhumell zoom is the best eyepiece in my collection (the Circle K zoom is a tad bit sharper at the 7.5mm setting, but has a much narrower FOV and annoying ghosting/reflections), and it is definitely the one that I use the most.