The Flawed Bird-Jones Optical Design
The Celestron ExploraScope 114AZ is a Bird-Jones 114mm f/8.8. It is optically identical to the Celestron AstroMaster 114EQ and Celestron 114 LCM, both 114mm f/8.8 Bird-Jones.
Bird-Jones optical systems are based on Newtonian reflector design but in most cases, they have a poorly designed and poorly manufactured corrector lens to fix the aberrations caused by the flawed spherical primary mirrors that Bird-Jones telescopes typically use in place of parabolic primary mirrors. It’s a nice design on paper, but Celestron’s implementation of the Bird-Jones design makes for a poor-quality scope, with mushy images at best and unusable ones at worst.
I’ve also found these scopes to be very difficult to collimate. Even when I manage to collimate them, the images still fall short of being sharp. Disturbingly, the ExploraScope manual neither tells me about the existence of collimation, nor how to do it, nor that the 114AZ needs it.
The focuser on the 114AZ is a usable 1.25” rack-and-pinion unit made almost entirely out of plastic. I use an additional shim on the drawtube as it seemed to wobble a little during my usage, but the focuser is functional as-is. I did this modification only because it was very cheap and easy to do it myself.
The Poor-quality Eyepieces
Like the AstroMaster and PowerSeeker Newtonians, the ExploraScope 114AZ comes with a 20mm erecting eyepiece of a Kellner-like design, a low-quality 4mm Ramsden eyepiece that provides too much power for the scope to handle, and an outrageously bad 3x Barlow lens made entirely of plastic.
Of these, only the 20mm eyepiece is usable, and even that is not a great eyepiece.
The 20mm’s cheap erecting design and low-quality coatings result in a lot of light loss and dim images. This stupid “erecting” eyepiece design is provided solely for the function of advertising the scope for terrestrial viewing because Celestron has a habit of marketing their cheap scopes at “nature/science” stores and other places where the consumer’s knowledge is basically limited to what the scope says on the box.
Also, the field of view is quite narrow at 35 degrees or so, and the 50x magnification it provides is a little too much for a low-power eyepiece. The eyepiece also results in even fuzzier images than what is already provided by the telescope’s Bird-Jones optics.
A 32mm or 25mm Plossl is an order of magnitude better than the 20mm erecting eyepiece, as is a decent Plossl or even a Kellner eyepiece for higher magnification.
The StarPointer red dot included with the ExploraScope felt ideal for such an instrument and works well. I could easily detach and reattach it with the two-hand knobs that are provided if needed for transport.
Lastly, the ExploraScope is offered with a smartphone adaptor that grips our phone and eyepiece and has adjustments to centre our phone’s camera. I could take some relatively sophisticated lunar photos with these, but the planets are difficult to shoot without a mount with tracking, and a CCD/CMOS camera or DSLR would be arguably better for such a task.
AltAz Mount
The ExploraScope mount is an alt-azimuth fork design on a lightweight (but sturdy) extruded aluminium tripod.
Due to the way these mounts operate and the scopes they are designed for (long refractors), it was rather hard to get the desired fine motion capability with a very short optical tube like the Celestron ExploraScope 114AZ. But it does work acceptably.
In my experience, it’s nowhere near as good as a Dobsonian or a good equatorial mount. And it also results in a lot of frustration when trying to keep the scope aimed at a target at high magnification.
Should I buy a used Celestron ExploraScope 114?
Unless it’s free, you really shouldn’t bother with a used Celestron ExploraScope. It’s not worth much of anything..
Aftermarket Accessory Recommendations
Despite the cost, which could, of course, go towards upgrading to a better telescope, quality aftermarket eyepieces can at least allow the observational experience with your ExploraScope 114AZ to be somewhat enjoyable, despite its imperfect optics. A 32mm Plossl (31x) yields the broadest possible field of view with the scope and is perfect for observing deep-sky objects, though it will display slight vignetting due to the Bird-Jones corrector lens, while a 15mm “redline” or “goldline” eyepiece (67x) should still be capable of producing sharp images and unveiling some planetary details without exceeding the limitations of the ExploraScope’s optics. You can also use these eyepieces with a better telescope in the future.
What can you see with the Celestron ExploraScope 114AZ?
The Celestron ExploraScope 114AZ is far from being a particularly good telescope, but if you make some serious effort to get the thing collimated and are understanding of its limitations, there’s still a fair amount to see.
- The Moon still looks fairly good and will amaze a beginner even with a poorly-collimated instrument.
- Mercury’s phases are likely to be difficult to spot with the ExploraScope 114AZ.
- Venus’ phases should be easy.
- Mars is likely to be a red dot devoid of detail. During the few months when Mars is close to Earth every two years, a properly collimated 114AZ may just barely be able to show you an ice cap and a dark marking or two.
- Jupiter’s moons are easily visible, along with the planet’s two main cloud belts. The Great Red Spot and the brown polar zones are more difficult to see, but they are possible to see.
- Saturn’s rings are visible, and its largest moon, Titan can be seen. Cloud belts on the planet itself are tricky, as are the other bright moons (Rhea is the easiest of the bunch). The Cassini division is probably not visible due to the 114AZ’s poor optical quality.
- Good luck finding Uranus and Neptune, let alone distinguishing them from stars.
- Globular star clusters are fuzzy balls with maybe the tiniest hint of graininess.
- Open star clusters are pretty, though the stars are less-than-sharp and could be framed better with the wider fields of view possible with faster (and better) tabletop Dobsonians.
- Bright nebulae such as Orion and the Lagoon look quite good, especially under fairly dark skies.
- Planetary nebulae are largely out of reach with the 114AZ, with a few exceptions. The ring is tiny but bright, the dumbbell is fairly large but dim, and most others are likely to be invisible or unrecognisable.
- Galaxies are simply too small and dim to be of much interest in any 4-inch telescope, let alone one with poor optics like the 114AZ. You’ll be lucky to see the brighter Messier catalogue galaxies and maybe the dust lane in M31.
