However, they are all significantly different in particular 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 BHZ is the only one 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 respectively). I have no data for the
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.
I got a chance to test the BHZ 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
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
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
Celestron #93230 8-24mm and Meade 4000 Zooms
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 convincingly wide and pleasant 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. 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
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
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 (550g). 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 it doesn’t come with included extras although it is supplied with a large bolt case. It also features a twist-up eyeguard and the zoom mechanism works smoothly with no click-stops. The mechanism, which utilises a waterproof seal, feels a little stiff at first but improves with use. 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 aftermarket Baader adapters. In this way the twist mechanism wouldn’t work the eyepiece loose. Pentax claim that the
Pentax XF 6.5mm to 19.5mm Zoom
The smaller XF sibling has a 6.5mm to 19.5mm focal length and an