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Zoom Comparison

Discussion in 'Eyepieces, Barlows, and Filters' started by Mak the Night, Jul 30, 2019.

Zoom Comparison

Started by Mak the Night on Jul 30, 2019 at 7:34 AM

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  1. Mak the Night

    Mak the Night Well-Known Member

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    1.jpg

    After some thought and deliberation, and over a period of time, I finally acquired six zoom eyepieces. The first four were a Baader Mk IV Hyperion Universal - Zoom, a Celestron #93230 8-24mm, a Hyperflex 7.2mm-21.5mm and a ‘Sky-Watcher’ 7-21mm. These are the first zoom eyepieces I have ever owned and I wasn’t totally sure what to expect. I’d read good reviews about the Baader and the Celestron and although there are a few others on the market these two generally seemed to be among the most popular choices. I am pretty convinced that the Celestron Zoom is identical to the comparable Sky-Watcher 8-24mm Zoom and are probably produced by the same OEM (possibly Synta or Barsta). Both the Celestron and Baader zoom eyepieces ostensibly magnify in marked stages. The Baader has five of 24mm, 20mm, 16mm, 12mm and 8mm marked gradations whereas the Celestron has four of 24mm, 18mm, 12mm and 8mm. The Sky-Watcher 7-21mm eyepiece was the least expensive of the three and and has 7mm, 9mm, 11mm, 15mm and 21mm marked magnification stages. On all of the zooms any magnification between the shortest and longest focal lengths can be achieved but only the Baader has definite (but subtle) click-stops.

    However, they are all significantly different in certain ways. Primarily in their respective retail prices. With the Hyperion basically being twice as expensive as the Celestron unit, which in turn was twice the retail price of the Sky-Watcher. The Baader is larger and heavier than both the Celestron and Sky-Watcher zooms. The Hyperion is the only one of the four that can utilise a 2” skirt even though it is technically only a 1.25” eyepiece. The Baader zoom apparent field of view varies between 50° and 68° while the Celestron varies between 60° and 40° (according to Baader and Celestron). I have no data for the AFOV of the Sky-Watcher zoom. Apart from an undercut it appears to be almost identical to the now discontinued Orion Explorer II 7-21mm Zoom. Orion claim an apparent field of view of 30° at 21mm and 43° at 7mm. There is a TS Optics equivalent to the Sky-Watcher zoom. TS Optics claim 50° at 21mm and 40° at 7mm. There are alternative claims of a purported 54° (at 7mm) to 38° (at 21mm) for the same eyepiece.

    Baader Mk IV Hyperion Universal - Zoom

    The first zoom I received was the Hyperion. Not uncommon with Baader products it comes supplied with various extras and I also purchased the 2.25x Hyperion Zoom Barlow at the same time. The first thing that I noticed was that the eye lens dust cap on the zoom eyepiece wasn’t easy to remove. This can be an important issue for me as I am physically disabled. This was later rectified when I had to return the zoom to the retailer when a huge piece of internal debris dropped into the field of view effectively rendering the eyepiece useless. The retailer rapidly replaced the faulty zoom, and the new one not only seemed to work perfectly, but had a much better fitting eye lens cap.

    2.jpg

    I got a chance to test the Hyperion Universal - Zoom first during a rich field session with my modified ST102. I decided to take only two eyepieces out with me, the other being a 31mm Baader Hyperion Aspheric. This certainly simplified things for me as I could now easily get both eyepieces, the OTA, finder, and diagonal all in the same carrying bag. The zoom replaced the usual rich field kit of a 19mm TeleVue Panoptic, a 14mm Baader Morpheus aka ‘The Dalek’ and a 9mm Celestron X-Cel LX (or alternatively sometimes an 8mm TS Optics Planetary HR). Inevitably most of the session was with the Hyperion ‘Super Dalek’. The transparency wasn’t too good although the overall seeing seemed like a decent Antoniadi ‘I’. The first thing I noticed was the smaller FOV compared to the 76° Morpheus, although I did actually expect to see a difference. I am not too sure of Baader’s claims of eye relief distance as I discovered that this varied with magnification. I seemed to be pushing my eye right into the eye lens quite often to see all of the FOV. The Pleiades and other open clusters looked very sharp even at higher magnifications. There was very little edge distortion and the overall image was very clear with a pleasing flat field. Zooming in on Caldwell 14 (Perseus Double Cluster) and double stars was great fun. Cor Caroli looked quite resplendent at 62.5x and was easily as good as with the 8mm Planetary HR.

    Sky-Watcher 7-21mm Zoom

    The Sky-Watcher ‘baby’ zoom is probably the sort of eyepiece that those who generally denigrate zooms are referring to. It is a small, lightweight and compact unit roughly 8cm tall (not including eyeguard height). As a consequence the field of view is somewhat diminished compared to the other three. Mine actually has no brand name on it. The housing appears adequately constructed with a chromed brass drawtube that includes an undercut. In my experience the undercut was not problematical. The rubber eyeguard is similar to the one on the Celestron 8-24mm EP and can also be rolled down. At first in use I tended to prefer it in the rolled down position for the shorter focal lengths. If you’re not careful the eyeguard can suddenly pop up from that position and smack you in the eye! I find when observing at around 21mm to 15mm the eyeguard is better in the default rolled up position as the eye relief seems quite long.

    3.jpg

    First light was on a twilight setting Moon in a 90mm Orion Maksutov giving me between 59.5x and 178.5x. Due to the conditions the best magnifications I achieved were about 90x to around 130x. It directly compared well with 14mm and 20mm Bresser 60° ‘Plossls’, although the field of view of the zoom was smaller of course. Occasionally I could detect some false colour right at the edge of the field stop. I next got to use it with a Sky-Watcher 72ED Evostar DS-Pro. My original plan was to start with low power rich field observing and then use the zoom paired with a Barlow on the Moon when it had risen high enough. Due to the fact I’d miscalculated the low lunar altitude I ended up using the baby zoom on its own (sans Barlow) for some unintended deep sky observing. First target was the Perseus Double Cluster, followed by several of the open clusters in Cassiopeia. I then turned towards the Beehive Cluster and some double stars, including Cor Caroli. The baby zoom gave between 20x and 60x on the ED72. I directly compared the zoom set at approximately 12mm with a 12mm Celestron X-Cel LX on the Beehive, Double Cluster and Cor Caroli. The zoom surprisingly held up very well and only showed any astigmatism right at the edge of field. The zoom action is smooth and easy to operate. This is a nice little zoom, although personally I would prefer to use it for lunar and planetary observing. Its small FOV would generally tend to preclude it being used for open clusters even though it did cope quite adequately in the ED72. Overall the Sky-Watcher zoom is well worth what it cost.

    Celestron #93230 8-24mm Zoom

    I didn’t originally purchase the Celestron to be used with a Barlow in the ST102. I had envisioned it as a back up or alternative to the Hyperion if the Baader zoom hadn’t worked out. However, it performed admirably paired with a 2.5x Celestron Luminos Barlow, giving wide views of the Moon. The Celestron housing is about 10cm tall (eyeguard rolled down) and 4.5cm wide with a chromed brass drawtube with an undercut. I found that I tended to prefer the eyeguard in the default rolled up position at 24mm.

    4.jpg

    There was also a slight amount of kidney beaning if the eye positioning wasn’t just right at the longest focal length. The ‘baby’ Sky-Watcher by comparison stands at 8cm (eyeguard rolled down) and is about 4cm wide. Furthermore, the Celestron zoom feels well made and substantial belying its reasonable price. At shorter focal lengths the FOV appears like a good 60° although the 40° is distinctly noticeable at 24mm. The Celestron #93230 is supplied with a nice and practical ‘vase’ shaped plastic container with a threaded screw-off lid. It also performed well in a 127mm Sky-Watcher Maksutov. The range was 62.5x to 187.5x although the most useful magnifications for lunar viewing were between around 125x to 187x (12mm ~ 8mm).

    Hyperflex 7.2mm-21.5mm Zoom

    This was a nice lightweight zoom eyepiece and performed well on lunar and planetary targets, although I tended to use it in conjunction with a Barlow. Unfortunately I had to return two in quick succession because of visible debris. I didn’t purchase a third. They are sold under a variety of brand names.

    5.jpg

    The next two zoom eyepieces I acquired were a TeleVue 3-6mm Nagler and a Pentax XL 8-24mm.

    TeleVue 3-6mm Nagler Zoom

    I realised that this zoom was perfect for my telescope focal lengths. It is beautifully made and the zoom mechanism works perfectly. There are definite click stops between the focal lengths although any length can effectively be selected between 6mm and 3mm. As you would expect this is a small 1.25” eyepiece and has a correspondingly close eye relief of about 10mm. The FOV on all focal lengths is a constant 50º. It’s not often that I’m totally astounded by an eyepiece, but I am by this. It is par-focal so zooming in for high planetary observing is nicely straightforward. I had a recent view of a twilight Jupiter with this zoom and my 102mm Altair Starwave.

    6.jpg

    The clarity and sharpness were outstanding. Even at 238x it wasn’t a bad image, although that was definitely pushing it in the conditions. However, I just couldn’t resist it. The ability to start at 119x and gradually increase the magnification until I achieved a balance between magnification and clarity with it was most satisfying. Later I split double stars, including the Double Double.

    Pentax XL 8-24mm Zoom

    I believe this was originally intended for a Pentax spotting scope. Which I find a bit weird as it weighs in at over half a kilo (550 g). It is also 1.25” and ranges from 24mm to 8mm. Ostensibly it is very similar to the Baader, although it has a substantially heavier and stronger build, and is apparently waterproof. It has no 2” skirt option. The Pentax almost feels like you could drop kick it without causing it any damage (I didn’t try this). Unlike the Hyperion Universal it doesn’t come with included extras.

    7.jpg

    There is a large bolt case supplied though. It also features a twist-up eyeguard and the zoom mechanism works smoothly with no click-stops. The mechanism itself feels a little stiff at first but improves with use (possibly due to the waterproofing O-ring). This is a fairly weighty eyepiece so I placed the drawtube barrel into a 1.25” (two screw) Baader adapter in a 2” diagonal. Most of my scopes and all of my refractors have after market Baader adapters. In this way the stiffish twist mechanism wouldn’t work the eyepiece loose. Pentax state that the FOV starts at 38° at the longest focal length then opens up to 60°. Which seems about right. The optics (six elements in four groups) in this eyepiece are excellent and include Lanthanum glass. The eye relief is consistently good, better than the Baader, and the brightness, contrast and clarity are outstanding for a zoom. I had the best image I’ve ever seen of the Ring Nebula with the XL. This zoom has a distinct edge on the Baader in many respects. I’m fairly convinced that this is the best zoom eyepiece of its class.
     
  2. Mak the Night

    Mak the Night Well-Known Member

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    The TeleVue and Pentax zooms were first tested using a 102mm Altair Starwave.

    starwave.jpg
     
  3. jgroub

    jgroub Well-Known Member

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    The Celestron and Meade 8-24mm zooms are identical. And I don't mean "identical"; I mean IDENTICAL.

    We have trouble telling which is which here in the scope shop.
     
  4. Mak the Night

    Mak the Night Well-Known Member

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    I suspected so, although more than one person has told me this. The Meade zooms I've seen have a slightly different design housing, which I assume is just a cosmetic difference.

    I've only been using zooms this year. I doubt they'll really replace my other eyepieces just yet. They are a lot of fun though and can save some time and frustration when changing eyepieces.

    The main disadvantages are the limited fields of view and overall viewing and build quality when compared to other premier eyepieces.

    Having said that the TeleVue, Pentax and Baader zooms visually equal any conventional eyepieces I own. The HyperFlex was a bit of a disappointment in quality control. In fact I was convinced it was made by Barsta because of the visible debris. I've been informed that they are most likely Kunming United Optics.

    kunming.jpg

    I'm fairly convinced these 2" dielectric diagonals are Kunming (the top diagonal was included with my 80mm Evostar).

    QKqI3CM.jpg

    I believe my William Optics bino's and 20mm SWAN's (seen above) are also KUO. The SWAN's in the picture aren't the 20mm WO's included with the bino unit.

    WT3vIPd.jpg

    The 'Celestron' and 'Sky-Watcher' were pretty good for the money though.

    qFVPhgj.jpg

    I tend to use these on my Mak's for lunar/planetary observing.
     
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  5. Mak the Night

    Mak the Night Well-Known Member

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    Here's a first. I managed about 90 mins last night with my ST102 before the clouds came. Transparency was patchy with a few clouds. I only used one eyepiece in the session; the Baader zoom!
     
  6. Ed D

    Ed D Well-Known Member

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    Excellent report, Mak. I really enjoyed reading it, and the pictures are a very nice touch, too.

    Thanks,
    Ed
     
  7. Mak the Night

    Mak the Night Well-Known Member

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    Thanks, and you're welcome Ed.
     

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