Overview Of Astromaster 76EQ Optical Tube Assembly
The Celestron AstroMaster 76 optical tube is a 76mm (3-inch) f/9.2 Newtonian with a spherical primary mirror.
A 76mm f/9 sphere deviates only very slightly from a parabola, so it works just fine. This is not the case with larger, faster focal ratio telescopes with spherical primary mirrors, where a significant lack of sharpness and definition happens, making the telescope almost unsuitable for astronomical purposes.
The only optical drawback I’ve noticed with the AstroMaster 76 is its diminutive size. By the time we account for light loss from the mirrors and the secondary mirror’s obstruction, the Celestron AstroMaster 76EQ newtonian reflector performs only as well as a 60mm refractor. I consider a 60mm refractor quite small, but because they don’t need collimation and tend to be offered at a lower price than the AstroMaster 76EQ, I would probably take the refractor.
However, the 76EQ does offer some advantages to us over a similarly priced 60mm refractor:
- There is no chromatic aberration on reflectors, giving them better planetary and lunar performance, all other things being equal.
- Reflectors typically have a shorter focal length, which gives them a wider field of view and lower magnification power with any given eyepiece.
Both the primary and secondary mirrors can be collimated. This is a feature that, although required, somehow isn’t always available with most of the cheap small Newtonians that I’ve reviewed.
An annoyance I’ve encountered with the AstroMaster 76EQ is the focuser drawtube unnecessarily poking into the light path when it is racked all the way in, as shown in the picture below.
Usually, while a telescope is being used, it’s racked out enough for this to not be a problem. But with some eyepieces that I had in my kitty, the focuser eclipsed the incoming light from hitting the scope’s primary mirror by quite a bit. Since this was bothering me, I removed the drawtube (which is quite easy), chopped the offending portion off with a hacksaw, and reinstalled it with absolutely no negative impact on the telescope’s functionality.
The other fault of the optical tube is that it has an extremely short dovetail bolted directly to the tube. There is thus no way for me to rotate the tube to a more comfortable position or balance it when I’m using heavy eyepieces or accessories. The inability to rotate the tube is annoying and I thought I should point it out.
The mount is capable of taking other telescope optical tubes that use the same dovetail saddle mechanism. But a different optical tube would likely cost more than the entire Celestron AstroMaster 76EQ unit.
Mixed Feelings on Eyepieces Provided
Like all other AstroMaster Newtonians, the Celestron AstroMaster 76 EQ comes with a cheap, narrow-field 20mm eyepiece. I would recommend replacing it with a 32mm or 25mm Plossl as soon as possible to get the most out of this telescope.
This 20mm eyepiece provides me with too much power (35x) to be a “low-power” eyepiece for a 76mm telescope. It also has a narrow, straw-like field of view. Furthermore, its useless erecting optics and cheap coatings absorb a lot of light and degrade the image quality.
The other included eyepiece is a 10mm Kellner, which provides 70x. It’s a pretty decent eyepiece, I’d say, from what I’ve experienced, albeit largely made of plastic. Though not my favorite, considering the scope’s sub-£200 price point, I’m willing to give it a pass.
The Rock-Solid CG-3 Mount
The mount supplied with the AstroMaster 76EQ is referred to in some literature as the “CG-2,” but it is identical to the mount supplied with the larger AstroMasters, which Celestron terms the CG-3.
If you ask me, the CG-3 is an overkill for the featherweight 76mm Newtonian optical tube. But it certainly does a great job. The scope is rock-solid, and I have zero complaints about its stability.
The CG-3 can be motorized with Celestron’s Logic Drive for hands-free tracking. Forget astrophotography, though. Any kind of camera will make the scope top-heavy and there’s no way to balance it, in addition to the fact that this is an f/10 scope on a relatively simple mount with only a partially metal focuser.
Alternative Recommendations
For the same price as or a little more than that of the Celestron AstroMaster 76EQ, we’d probably recommend a tabletop scope: either the Zhumell Z100 or the Sky-Watcher Heritage 100P, essentially identical scopes with a bit more aperture and far superior accessories. If you can expand your budget, the Zhumell Z114 is even better.
For additional options that might be right for you, check out our rankings.
Aftermarket Accessory Recommendations
Apart from its small aperture, the AstroMaster 76EQ is acceptable performance-wise, but the provided 20mm erecting eyepiece of course kills any chance of decent low-power views. A 32mm Plossl (22x) is far better and provides the widest possible field you can get with the 76EQ, perfect for deep-sky viewing, while a 6mm redline or goldline eyepiece (117x) provides the maximum useful magnification with this telescope – ideal for viewing the Moon, planets, and double stars. You can also fit the AstroMaster CG-3 mount with Celestron’s Logic Drive for automatic motorized tracking if desired.
Astrophotography Capabilities
Apart from simple phone shots, forget any kind of astrophotography with the Celestron AstroMaster 76EQ reflector telescope. The scope is too small in aperture to do useful work with a CCD camera for planetary imaging (a CCD would also cost more than the entire telescope), and a DSLR will strain the focuser and mount as well as render the telescope unable to balance properly.
For a sub-£200 telescope, though, this is all to be expected.
What can you see with the Celestron AstroMaster 76EQ?
The 76mm aperture of the Celestron AstroMaster 76EQ telescope is only enough to show you the brightest deep-sky objects, but it will do a reasonably good job of observing the Moon and planets. With the AstroMaster 76EQ, expect to see:
- Mercury’s phases, with effort and luck
- Venus’ phases
- Lots of details on the moon
- One or two dark patches on Mars when it’s in opposition every two years.
- Jupiter’s moons, cloud belts, and Great Red Spot
- Saturn’s rings, its moon Titan, and maybe the Cassini Division and some banding on the planet itself with good seeing.
- Uranus and Neptune as turquoise and azure dots
- The Orion Nebula, the Ring Nebula, M13, the Pleiades, and a couple dozen of the other brightest deep-sky objects.
- Many double stars
