Celestron NexStar 6SE vs. NexStar 8SE

Photo of author
Written By: Zane Landers
Category: Learn

The Celestron NexStar 6SE and Celestron NexStar 8SE are the larger two models of the NexStar Special Edition (SE) line of catadioptric telescopes offered by Celestron. These telescopes are both computerized Schmidt-Cassegrains on alt-azimuth mounts, with 6” and 8” apertures, respectively. Readers who have seen our rankings may be curious as to why the 8SE receives much less acclaim from us than its smaller counterpart, or perhaps you’ve found this article while attempting to decide between the two.

NexStar 6SE vs 8SE

The NexStar 6SE and 8SE are entirely identical, apart from using different telescope tube assemblies: the C6 XLT for the 6SE and the C8 XLT for the 8SE, respectively. Their mounts, accessories, and basic design parameters are identical. However, unsurprisingly, the larger 8SE telescope tube is heavier than the 6SE’s, pushing the limits of the provided mount. The 8SE is noticeably inferior to the 6SE for this reason. Without further ado, let’s get into a more detailed comparison.

ScopeApertureMount TypeMax FOVMaximum MagnificationStabilityQuality

Bottom Line

The Celestron NexStar 6SE and 8SE are far from our top picks in their respective price ranges, and if you’re looking to buy your first telescope, we recommend perusing our rankings and Best Telescopes (or Best Computerized Telescopes) pages if you haven’t already. If you are really sold on the Celestron NexStar 6SE or NexStar 8SE, we would also recommend you consider one of the Celestron NexStar Evolution models (6″ or 8″) instead. The 6SE is a good enough scope among the two, but there are better options to be had given its price point these days. The 8SE is visibly lacking in stability, and we do not really recommend you buy one unless you simply lack any better alternatives.

Optics Comparison

The Celestron NexStar 6SE and 8SE are both Schmidt-Cassegrain telescopes with a focal ratio of f/10. The 8SE is based on Celestron’s original 1970s C8 optical tube – albeit modernized with HyperStar compatibility and Celestron’s “StarBright XLT” coatings. The C6 XLT, on the other hand, only debuted in 2005 but is, in essence, a scaled-down C8 XLT. Both use an f/2 spherical primary mirror and a secondary mirror with a convex curvature that amplifies the focal length by a factor of 5. The Schmidt corrector at the front of both telescopes is similar in design and manufactured with the same techniques, and the central obstruction of both by the secondary mirror is around 33% by diameter.

Of course, the aperture difference between these two scopes is the defining characteristic that separates them. The C8 XLT offers about 75% more light-gathering power than the C6 XLT thanks to its larger aperture and boasts about 30% more resolving power. On the other hand, the C8 needs more time to cool down to ambient temperature owing to its larger optics and has a longer focal length of 2032mm vs. 1500mm, which leads to higher magnifications and a narrower field of view with a given eyepiece.

The C8 and C6 are both compatible with standard Schmidt-Cassegrain threaded accessories, including a 2” diagonal. However, neither telescope fully illuminates a 2” field thanks to the size of the secondary mirror and internal baffling inside. The C8 XLT will vignette with eyepieces over a 35mm field stop; the C6 vignettes with over a 27mm or so. Thus, it is completely pointless to use 2” eyepieces with the C6/6SE and the C8/8SE barely benefits from the use of the 2” format. The unvignetted field of view of each is basically the same, however – about 1° of sky, or twice the angular diameter of the full Moon. Using an f/6.3 reducer will not enable a wider, unvignetted field of view.

The EdgeHD version of the C8 does not share the standard C8’s vignetting problems and is designed to illuminate a full 2” field at its native f/10 focal ratio, but it is not offered with the NexStar SE mount. However, the Celestron NexStar Evolution 8” EdgeHD telescope is available.

Both the C8 XLT and C6 XLT are compatible with Starizona’s HyperStar lens/adapter system to turn either telescope into an f/2 Schmidt Camera for wide-field astrophotography, converting the C8 and C6 to 390mm and 300mm focal lengths, respectively. However, as is the case with vignetting at the normal focus of these telescopes, the C6 and C8 end up having essentially the same unvignetted field of view with Hyperstar (about 4°). Additionally, the inevitable extra obstruction by your camera/accessories ends up practically reducing the C6’s focal ratio when used with the HyperStar configuration, which means that there is really no advantage to using HyperStar on the C6 over the C8 – especially given the pricing.

The identical focal ratios and basic optical/mechanical parameters (apart from size) implemented in the C6 and C8 mean that things like image shift, focus/collimation tolerances, etc. are essentially identical. However, the average C6 seems to be quite a bit better optically than the average C8. This is probably because the tooling used to manufacture the optics for the C6 – particularly the Schmidt correctors – is newer and used at a lower volume than that for the C8, leading to a smoother polish on some of the optics and perhaps a little more care as to quality control. 

The idea that the C6 is produced with less or to tighter tolerances than the C8 might sound odd when you remember that the C6 – both as an optical tube and packaged with mounts like the NexStar 6SE – is quite a bit cheaper than the C8. However, the C8 is more popular, available in more configurations, and has been available for a longer period of time than the C6. That means that there are more C8 XLT optical tubes than C6 ones, even just from the starting point of 2003-2005 when the present-day C8 XLT began production in China (there are vastly more C8s overall than the C6, since the C8 debuted in 1970). After all, if you’re reading this article, you may have considered jumping the gun and getting the 8SE over the 6SE yourself.

Without a doubt, in terms of general and deep-sky performance, the C8 easily beats the C6. However, under typical seeing conditions, a C6 may beat out a C8 for viewing fine detail on the planets and resolving close double stars, or at least get close. This can happen if the particular C6 unit is overall better optically and/or turbulent atmospheric conditions do not allow for one to utilize the full resolution of an 8” instrument.

Accessories Comparison

The NexStar 8SE and 6SE both come with a red dot finder for aiming, a 1.25” Schmidt-Cassegrain visual back, a 1.25” prism star diagonal, and a 25mm “E-Lux” 1.25” Plossl. This eyepiece has a roughly 52-degree apparent field of view, thus providing 61x and a 0.85° field with the 6SE or 81x and a 0.64° field with the 8SE, respectively.

The accessories included with both the 8SE and 6SE are fine, but both would benefit from a 32mm Plossl over the 25mm for the maximum possible field of view with a 1.25” eyepiece, and you, of course, will need additional oculars for higher magnifications.

Mountings Comparison

The Celestron NexStar 8SE and 6SE use a larger variant of the single-armed NexStar SE alt-azimuth mount. Compared to the 5SE/4SE design, the fork arm is longer, the base is wider, and the tripod features no wedge and thicker 1.5” legs over the 1.25” legs of the 5SE/4SE mount. This mount is (as of the time of writing) well over 15 years old and still utilizes Celestron’s NexStar+ controller (though a WiFi dongle can be added if you wish).

The larger NexStar SE mount works just fine with the 6SE. While not able to be aimed manually, the tracking, pointing, and stability are more than adequate, and the whole assembly is lightweight and easy to carry fully assembled if you need to. The 8SE, on the other hand, is a far different picture.

The C6 XLT optical tube is about 8.5 lbs; the C8 XLT is 13.5 lbs before you add any heavy eyepieces or a dew shield. This is a problem since the NexStar SE mount is not really capable of supporting loads over about 11 pounds even without extending the tripod legs. The single fork arm itself lacks stiffness owing to its mostly plastic frame, while the 1.5” diameter tripod legs are wobbly and twist under the weight of the C8 XLT telescope tube and the mount head. The lightweight nature of the NexStar SE mount/tripod also means that the 8SE configuration is extremely top-heavy, further reducing stability.

The Celestron NexStar 8SE’s lack of stability may not even bother newcomers who are used to shaky, low-quality camera tripods or cheap, low-quality telescopes. This is the primary reason that the 8SE usually gets plenty of acclaim, even from genuine hobbyists. Likewise, anyone who hasn’t actually owned or used an 8SE could easily be mistakenly convinced that there are no stability problems, especially based on hearsay.

Nonetheless, the NexStar 8SE is unsteady enough that we don’t encourage you to buy one. The wobbliness reduces the accuracy of the telescope’s pointing and tracking by enough that you will notice on a longer night of observing, and while the slight wiggles at 81x might not be much of an issue, it becomes frustratingly hard to focus at all when employing magnifications upwards of 100x, 200x, and so on; similarly, it can be hard to collimate the 8SE’s optics on a star due to the bouncy nature of the mount.

Leave a Comment