Equipment Review (preliminary)

General Impression

Advertised as beginner's telescope this short-tube OTA surprises with fine optical quality given it is a simple achromatic (optically imperfect) design. With its Ø80mm aperture and 400mm focal length it is a standard f/5 design aiming at observation of star clusters, galaxies and nebulae. Its focal length is too short for planets, but the small moon looks pretty through a quality eyepiece.

According to the manufacturer, the Starquest 80 has "Coated Optics", in that we do not know whether it is single side coated or, more likely, multi-coated.

Attached to the OTA is a 80mm Vixen-style dovetail plate which is okay for visual use on a tripod or mobile tracker but insufficient for balancing with an attached camera (well it is not an astrograph). The dovetail has two 1/4 inch threads for mounting on a tripod.

Mounted inside the OTA is a baffle ring playing a crucial role in reducing stray light by blocking unwanted light paths, minimizing internal reflections and improve contrast.

The barrel is made of metal, yet keeping the telescope lightweight (1.3kg) and portable. Its sturdy construction helps maintain optical alignment. Only the lens cell is made of plastic.

Chromatic aberration (color bleeding) cannot be overlooked, in particular and naturally at higher magnifications on bright objects, but it is actually little for an f/5 achromat providing decent color correction for its price range.

Focuser and Accessory Interface

The focuser is surprisingly smooth and rigid, a real bonus. It travels 60mm and can be fixed with a screw without tilting the draw tube. The back focus plane lies 139mm away from the rear of the barrel, explaining the short tube of 355mm including the length of the non-expandable, non-retractable dew shield. Therefore, a long extension tube (Ø42mm, L=80mm min) is required for a dedicated astrocam, while the focuser travel is just long enough for a DSLR reaching infinity focus without extension (the sturdy focuser comes in handy here). Extension is required even when using 0.75x and 0.5x reducers threaded on an astrocam.

The accessory mouth takes a 1.25" star diagonal (bundled) eyepieces is M42/0.75mm (male) threaded for a CMOS astrocam or a T-ring for a DSLR. A so attached camera can be rotated with a fix (mounting) ring located between the focuser and the accessory holder. It is a bit primitive, cost-saving solution but working well.

When using cameras, please bear in mind that, in general, long extensions and a widely rolled out focuser can cause tilt in the optical axis.

Focuser Travel for Reference

The idea is to use various magnifiers on the nose piece of an astrocam or an eyepiece without need for swapping extension tubes to reach focus. This is merely a guideline as flange back of cameras and position of focal planes in eyepieces vary. The final reduction or magnification factors depend on the distance of the reducer or barlow lens to the focal plane. Also, focuser mileage can vary with the type of the reducer or barlow, in that is hard to predict the effective focal length. In this example, the optical path of the extension is 65mm while the astrocam, Player One's Neptune-M, has a flange back of 12.5mm. The test eyepiece is a Baader 8-24mm zoom locked at 24mm. The focuser travel for each configuration is given in millimeters:

With an extension of 65mm you can use various magnifications without need for threading and re-threading extension tubes for reaching focus. Remember, the focuser is highly rigid. Also tested with fixed focal length eyepieces, 6mm, 12mm and 25mm. They all get into focus.

Extension tube + nose piece = 65mm

Optical Path of a Refractor

Included Eyepieces

The achromatic design balances cost and performance, making it a good entry-level telescope. However, at f/5, it’s considered a "fast" telescope, which can be less forgiving with lower-quality eyepieces, potentially showing optical aberrations like coma or astigmatism at the edges of the field of view with certain eyepieces.

The bundled 25mm and 10mm eyepieces are probably uncoated Kellner or Modified Achromat designs in plastic tubes, based on Sky-Watcher's typical offerings for entry-level telescopes. These eyepieces provide magnifications of 16x and 40x, respectively, and may show limitations in a fast f/5 system due to their simpler optical design. Kellner eyepieces might not be the best choice for telescopes with fast focal ratios (f/5 or faster) due to potential optical aberrations. For better performance, especially at the edges of the field, upgrading to Plössls or wide-angle eyepieces could enhance the viewing experience. To keep parts count low, a zoom eyepiece such as a common 8 mm (50x) to 24 mm (17x) will be fine, too.

Terrestrial Use

The Starquest 80 is also a fine scope for terrestrial observations, however, the included 90° star diagonal mirrors the view in that users may wish to replace it with a "45° Erect Image Diagonal" which delivers right side up and left-to-right correct images as if you're looking through binoculars when used with refractors for daytime terrestrial viewing. A reduction in the quality of an optical image (astronomical or terrestrial) is always associated with additional optics (mirrors and lenses), but quality parts will hardly introduce discernible issues.

Sample DSLR Image

Specification Overview - Starquest 80

Pros

• Smooth and rigid R&P focuser (excellent!)
• Generous 60mm focus travel
• Large Ø40mm focuser knobs
• Acceptable chromatic aberration
• Low OTA weight
• Attractive cost-performance ratio

Cons

• Focuser gear ratio a bit coarse for f/5.
• 80mm dovetail length is too short for balancing photographic gear.
• Finder base not precision machined, pointed fixing screw leaves scratches.
• Bundled eyepieces do not give justice to the fine objective lens.

Conclusion

Though not specifically designed for imaging, this achromat features a quality lens, delivering sharp and contrast-rich terrestrial views. Due to its simple — though inherently imperfect — optical design, the outer regions of the field of view exhibit green and violet fringing in the eyepiece. The bright moon and planets are framed by violet bleeding. However, a wide central circle remains nearly free of chromatic aberration. As a result, deepsky imaging is feasible with small sensors like the IMX585, IMX676, or IMX678, which capture only the central portion of the view. Additionally, narrow-band filters can help mitigate chromatic aberration. This achromat is an affordable, regret-free choice for novices in both visual observation and imaging. Its balance of quality and price makes it an appealing introduction to a hobby where everything can go wrong at once—but ultimately offers a motivating reward at the end of the day.