The 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 127EQ’s tube is only twenty inches long – 500mm. How does one fit a Newtonian optical system (not a Cassegrain, which folds the light path into a smaller physical package) into that small of a tube?

The answer is that the 127EQ 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 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 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 127EQ’s corrector is just a Barlow lens inserted into the focuser drawtube – not a proper corrector lens. It doesn’t fix the spherical aberration inherent in the roughly f/3.5 spherical primary mirror. It makes the light cone a little steeper, which in theory would correct the system to maybe half a wave – bad at half the tolerance required for a good telescope, but somewhat usable. But due to the positioning of the corrector, this isn’t possible.

To make matters worse, the PowerSeeker 127EQ’s primary mirror isn’t even a precise sphere, it’s a random shape that came straight out of the polishing machine.

The 127EQ primaries I’ve tested have had rough surfaces, really weird shapes, all sorts of microscopic holes and hills which damage the image, and 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.

Thanks to the corrector lens being permanently installed in the focuser, the 127EQ is extremely difficult to collimate.

You can remove the corrector and collimate it with a laser or the like, then re-insert the corrector, but this is a complicated procedure and heaven help you if you need to collimate it in the field. You’d think that the inability to collimate the scope would be the final nail in the coffin for the 127EQ delivering a decent image, but no…