Overview Of The 127mm Bird-Jones Optical Tube
The Celestron PowerSeeker 127EQ is a 127 mm 5ʺ f/7.87 (focal ratio) Newtonian with a focal length of 1,000 mm. If you do some basic math, you’ll immediately notice something odd. The PowerSeeker 127EQ’s tube is only twenty inches long – 500mm. How does one fit a “Newtonian” optical system (not a Cassegrain, which actually “folds” the light path into a smaller physical package) into that small of a tube?
The answer is that the Celestron PowerSeeker 127EQ is not a Newtonian. It’s a Bird-Jones. Bird and Jones were two amateurs in the 1950s who sought to create a simple telescope with a spherical instead of a parabolic primary mirror, with a corrector lens/Barlow in front of the secondary mirror. This design, in theory, can work well, and some properly executed Bird-Joneses do in fact work quite well. But the Celestron PowerSeeker 127EQ is anything but properly executed.
Unlike the classical Bird-Jones style, which puts the corrector lens just in front of the secondary mirror, the 127EQ’s “corrector” is mounted in the focuser. This means that it will move whenever you dial in the focus, thus assuring the correction is basically never spot-on.
Even if the corrector being mounted in the focuser was not an issue, the Celestron PowerSeeker 127EQ’s corrector is just a Barlow lens inserted into the focuser drawtube. This is not a proper corrector lens. It doesn’t fix the fact that the f/3.5 spherical primary mirror has a lot of spherical aberration, which makes it impossible for the telescope to make a sharp image even at very low magnifications. Rather, the corrector-Barlow simply makes the path of the light rays through the telescope a little steeper, which in theory might be enough to provide a pretty decent – if not the sharpest – image. But because it is mounted in the focuser, the 127EQ’s corrector is always moved away from its ideal position. This means that the scope can only produce images that are barely good enough for a telescope of its size and price. At worst, the views are a completely mushy, unusable mess.
To make matters worse, the PowerSeeker 127EQ’s primary mirror isn’t even a precisely manufactured sphere; it’s a random shape that came straight out of the polishing machine. The PowerSeeker 127EQ primaries I’ve tested have had rough surfaces and all sorts of microscopic holes and hills that damage the image, as well as many other complicated flaws. These are all caused by the fact that nobody actually bothers to test these things before throwing them in the telescope. If Celestron performed any quality control on the PowerSeeker 127EQ, after all, it might not have been created in the first place. The primary mirror also appears to be secured to its support with solid gobs of epoxy, which warp and distort the mirror due to the stress they induce on the glass. This further hinders the already limited capabilities of the telescope.
With the corrector lens in the focuser, it’s hard to collimate the Celestron Powerseeker 127EQ because the corrector makes the reflected images of the primary and secondary mirrors look very small. The corrector lens also inhibits the function of a laser collimator. So, to collimate the 127EQ, you must first remove the corrector lens. This means taking apart the focuser, carefully unscrewing the ring that holds the corrector, and being careful not to get fingerprints or grease from the focuser drawtube on the corrector lens. You can then temporarily put the focuser back together to collimate. After collimating the scope, you then have to take the focuser apart again, re-install the corrector, making sure to put it in the right way, and then re-assemble the focuser. The Celestron PowerSeeker 127EQ also has collimation screws that don’t move much and are easy to strip. Collimating the 127EQ was hard enough for me to do in the shop; a beginner attempting it out in the cold and dark will find it impossible.
Problems With Celestron Powerseeker 127EQ Accessories
If you thought the Celestron Powerseeker 127EQ’s optics were bad, the eyepieces are actually worse by every stretch of the imagination.
The 50x low-power eyepiece that comes with the 127EQ is a 20mm Kellner with a permanently installed “erecting prism” that flips the image right-side up. 50x is a bit of a high magnification for “low power” with a 5” telescope, especially one with poor optics. The erecting prism is included so that Celestron can claim the telescope is capable of terrestrial viewing, and it comes at the expense of sucking up quite a bit of the light entering the telescope, blurring the image due to its extremely low quality and providing a field of view reminiscent of a drinking straw. Because of this, it will be hard to find targets or fit them into the field of view. The included next-to-useless finderscope won’t help much with this.
For high magnification, the 127EQ comes with a 4 mm Ramsden. The last time a Ramsden had any place in an amateur astronomer’s eyepiece box was in the 1960s, when a Kellner or Orthoscopic was rare and sought after. Like the included 20mm eyepiece, the 4mm Ramsden has a tiny field of view. Worse, however, it has a tiny eye lens and next to no eye relief-meaning you’ll need to jam your eyeball into it to see much of anything-and provides 250x, which is too much for even a quality 5” telescope (which the 127EQ is a far cry from). It’s also generally low quality and would provide a mushy image anyway, even if there were not too much power for the scope to handle.
The included “3x Barlow” is a plastic-lensed abomination that exists to provide the “450x” Celestron claims the telescope is capable of (in actuality, very few telescopes are capable of, let alone used at, 450x). It is completely useless and should be discarded.
For a finderscope, the Celestron PowerSeeker 127EQ comes with a 5×24 unit with a single plastic lens and a plastic eyepiece. To get a usable image, the lens’s aperture is closed down to less than 10 mm. This takes away its ability to gather light. The bracket is also hard to align with the telescope, so the finder is almost always pointed in the wrong direction and is therefore useless. You’re better off removing the finder itself and using the bracket as a peep sight.
About The EQ-1 Mount
The EQ-1 mount provided with the PowerSeeker EQ telescopes is actually fairly respectable in terms of build quality and operation. But it can’t hold up a telescope as big as the Powerseeker 127. Not only is the mount very unstable when the 127mm optical tube is on top of it, but the counterweight that comes with the telescope is not heavy enough to keep it balanced. So, when using the 127EQ, you have to always lock up the mount axes a little bit to keep the whole telescope from moving around on its own. This means that as you move the telescope around the sky, the motions will be jerky and less than smooth, which makes the stability problems we’ve already talked about even worse. Between these issues and the terrible included finderscope, it is hard to get the 127EQ pointed at pretty much anything besides the Moon.
Should I buy a Used PowerSeeker 127EQ?
No, not even for $1.
Almost anything is going to be better than the PowerSeeker 127EQ; even a pair of 7×50 binoculars is likely to lead to more satisfaction in exploring the night sky. However, here are a few of our top picks:
- The Zhumell Z100 and Orion SkyScanner 100mm have less aperture than the 127EQ, but thanks to the ridiculously poor design of the 127EQ they of course easily best it in image quality. These telescopes – as with all others we recommend both feature parabolic primary mirrors with no internal corrector lenses, and quality accessories and mounts.
- The Zhumell Z114 and Orion StarBlast 4.5 Astro are both even better than the smaller 100mm tabletop scopes we also recommend, with the same great optics, accessories, and easy-to-use mounts. They are night and day compared to the awful experience of the 127EQ.
- The Sky-Watcher Heritage 130P offers slightly more aperture – and infinitely better views – than the PowerSeeker 127EQ, all in a convenient and portable package thanks to its collapsible tube. The included accessories are great, too.
- The Sky-Watcher Heritage 150P offers significantly more aperture than the 127EQ or smaller tabletop reflectors we recommend in its stead, with a surprisingly compact tube thanks to Sky-Watcher’s FlexTube collapsible tube design. A computerized version, the Virtuoso GTi 150P, is also available at a slightly higher price but still offers the freedom to be aimed manually if you wish.
- The Orion SkyQuest XT6 provides similar performance to the Heritage 150P, but with a solid-tubed design and a tube and base tall enough to not need a table. It’s a lot more rugged than a tabletop scope, but also a lot more of a hassle to move around. The similar Apertura DT6 and Sky-Watcher 6” Classic are also great choices, but the XT6 is our favorite of the three thanks to its features, price, and availability.
What can you see with the Celestron PowerSeeker 127EQ?
The Celestron PowerSeeker 127EQ’s low-quality optics are a permanent handicap, even if you upgrade the accessories. If you can manage to get the scope collimated and deal with the frustration of aiming it, expect to see the following.
- Mercury – An ill-defined smudge. It’s unlikely you’ll be able to resolve its phase.
- Venus – The phase is easy to see, albeit with a lot of glare surrounding the planet caused by the corrector lens and low-quality eyepieces.
- The Moon – A fairly decent view, but nowhere near as detailed as the sights delivered by a telescope with quality optics.
- Mars – An ill-defined blob even when it’s close to Earth. You might just be able to make out an ice cap and maybe a dark smudge.
- Jupiter – The moons are obvious (but then again, they’re obvious in a pair of cheap birding binoculars too). The two equatorial cloud belts are visible, albeit low in contrast. The Great Red Spot, normally a pretty easy catch with a careful eye and almost any half-decent telescope, is not sharply defined enough to spot.
- Saturn – The rings are visible, though fuzzy, and maybe a couple of moons can be spotted. The Cassini Division in the rings cannot be seen, and you won’t be able to glimpse any of Saturn’s fainter moons besides Titan and Rhea.
- Uranus and Neptune – Assuming you can even find them, the PowerSeeker’s optics are bad enough that you can’t distinguish either planet as a clear disk.
Many of the most exciting star clusters are visible, but lack crispness.
- Emission nebulae: The Orion Nebula looks okay but the Trapezium star cluster is mushy. The Lagoon is a wispy cloud, with bloated, ugly stars inside it. The Swan is ill-defined.
- Galaxies are troublesome to find and lack anything resembling detail.
- Forget most planetary nebulae; they’ll be blurred beyond recognition.
- Splitting any remotely close double star with the 127EQ is impossible.