I bought the Orion E-Series 7-21mm Zoom for £56.99. There are other zooms that appear identical to this eyepiece selling under other brand names. They undoubtedly originate from the same OEM. There doesn’t seem to be a great difference in their respective retail prices. The first thing that I noticed with the Orion ‘E-Series’ was how physically light it was.



The Orion website says it is 136g (although I weighed it at 150g) which would make it around 20-25g lighter than my unbranded ‘Sky-Watcher’ 7-21mm zoom of almost identical proportions. The E zoom is 94mm tall, 43mm wide, and I make the eye lens and field lens 25mm and 16mm respectively. Orion Telescopes and Binoculars claim a 16mm field stop. They also state that there are six elements with a 40.0° - 57.0° FOV and the lens edges aren’t blackened.



The housing and barrel are aluminium and the barrel has an undercut and a filter thread. The coatings seem fine and the other thing that I noticed is that it doesn’t seem to rattle as much as its ‘Sky-Watcher’ equivalent. In the past I haven’t had much success with 7-21mm (or thereabouts) zooms. The ‘Sky-Watcher’ 7-21mm zoom was prone to a bit more chromatic aberration than I can generally tolerate. My Pentax XF zoom (6.5-19.5mm) also displays some lateral colour on lunar and planetary targets.



At around 22:15 BST on the 27th of May there weren’t many twilight stars to observe. The transparency was decidedly below average, although according to some of my software the seeing was predicted to be good. I got first light with the E-Series zoom placed in a 3x BST Barlow with my modified ST80. This gave a range of around 57x to 171x. The target was a very visible Arcturus; the fourth brightest star in the sky. The rubber eyecup isn't easily folded down or removed but the overall ergonomics were satisfying. I found that the eyepiece was pleasant to use with no eye placement issues.



My first impression was that it was showing some chromatic aberration. I rapidly realised that this was a combination of the 0.2 magnitude of ‘ɑ Bootis’ and the fact that I was using an inexpensive achromat. I had a quick look at Vega, the fifth brightest star in the sky, and patiently waited for the night to get darker. As soon as I could discern ε Bootis through the poor transparency I decided to try and split it. The anxieties I had earlier about false colour were abated. The split at around 160x was very sharp and apparent. It appeared like the Orion had an acuity superior to my Celestron zoom. The magnitude 4.7 binary companion was very distinct and the colours of both stars were quite striking. I thought that the zoom mechanism itself was fairly smooth and precise. There is no clickstop indicator.



I then tried Cor Caroli which is an old favourite of mine. I was still impressed by the overall clarity and colour separation from a zoom in this price range. Next up were a rising Albireo and ε 1 & 2 Lyrae. The seeing may have been better than the transparency as the ‘Double Double’ was a particularly effortless split. All four stars were cleanly and sharply split even at around only 100x magnification. At 170x they were still incredibly bright and acute. I spent the next hour splitting other doubles until it inevitably clouded over.



I initially purchased this zoom primarily for double star observing while placed in a Barlow. It hasn’t disappointed me. The combination of light weight, relatively comfortable ergonomics, and visual acuity seems to belie its competitive retail price.