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Starfield’s Géar 90 Refractor Review: A Premium Apo for Visual and Photo Use

Apochromatic refractors abound on the market. The Géar 90 stands out by offering first-class optics for color-free views and images.

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The Starfield Optics Géar 90 EDT offers optics free of chromatic aberration in a tube fitted with solid CNC-machined components in plain black-and-white livery.  Credit: Alan Dyer

The Canadian company Starfield Optics has introduced a new line of triplet apochromatic refractors with premium Ohara FPL53 glass and all the mechanical features desired by visual observers and astrophotographers. While there is no shortage of “apos” on the market, I found that Starfield’s new Géar series does offer optical performance a cut above many lower cost apos, with a price still well below the prestige brand names.

The new Géar 90 EDT is a 90 mm aperture f/6 instrument visually. For photography I tested it with Starfield’s optional ($260 Canadian) 0.8x Adjustable Reducer, yielding an f-ratio of f/4.8 with a focal length of 432mm. A 1.0x flattener is also available ($155 Canadian) for imaging at f/6 when shooting at the native focal length of 540mm is desired.

The Géar 90 is the middle member of the current Géar apo family, which includes the smaller Géar 80 f/6 and larger Géar 115 f/7.

The dew cap can extend two inches, while the focuser has a range of 3.74 inches (95 mm). Credit: Alan Dyer

Géar 90 Fittings and Finish 

The Géar 90 is 17.75 inches (45 cm) long when collapsed with a dew cap that can extend for 3.25 inches (82 mm) in front of the 90 mm objective. The telescope weighs a modest 11.5 lbs (5.2 kg) with the optional reducer, so even with a camera and accessories it is suitable for use on smaller, affordable equatorial mounts.

The dew cap has a lock to keep it from sliding down when aimed up. The bolt for this is packed separately to prevent damage in shipping but, as the scope came with no instructions, it took me a while to figure out where that extra bolt should go until I noticed the threaded hole in the dew cap. Even unlocked, the dew cap did not slip, though.

The 9.7-inch (24.5 cm) long Vixen plate on the bottom has a slot and multiple holes, allowing for flexibility in where it can be mounted for balancing loads. Credit: Alan Dyer

The tube rings come with a Vixen-standard dovetail bar on the bottom and a handy handle on top. The handle is machined with Arca-Swiss standard grooves, though in astrophotography few accessories use that photo industry standard. The handle also has three threaded bolt holes, one with a 1/4-20 thread and two with similar but slightly finer M6 metric threaded holes. If these were plain, unthreaded holes it might be easier to attach accessories such as guidescopes that have their own threaded holes.

The focuser’s Synta dovetail shoe can accept small guidescopes such as Starfield’s own 30 mm Guidescope ($135) shown here. Credit: Alan Dyer

The focuser comes equipped with a Synta-standard dovetail shoe for accepting common accessories like finder scopes. The machined tube rings also have faces tapped with M6 metric-threaded holes for attaching other mounting plates or accessories.

The rack-and-pinion focuser has a lock plus threaded holes to accept motorized accessories. The large silver knob at right is for locking the included Camera Angle Adjuster. Credit: Alan Dyer

The 2.5-inch helical-cut rack-and-pinion focuser proved very smooth and accurate. It was an absolute pleasure to use, with its large coarse focus knobs and precise 10:1 fine focus adjustment. There was no wobble or image shift, and it held heavy loads securely with no slippage or focus creep, even with the focuser unlocked and the scope aimed high.

The entire focuser can rotate, with a large lock knob to secure its angle, plus tension screws to adjust how easy it is to turn when unlocked. I found I had to tighten these slightly, as even when locked the focuser tended to turn too easily when applying torque to it, such as when attaching a camera.

The Géar 90 comes with a visual back for 2-inch and 1.25-inch eyepieces and star diagonals. The dovetail shoe will accept red dot finders or finder scopes for visual use. Credit: Alan Dyer

The focuser also comes standard with a “Camera Angle Adjuster,” a rear rotator that works equally well with a star diagonal or camera, to allow turning an eyepiece to a desired angle for comfort, or a camera for framing. The Rotator has its own large lock knob which secured the rotation tightly. When loosened, though, it was easy to turn a camera, and with no change in focus position or sensor tilt.

I found no issues out of the box with images exhibiting defocused stars on one side of the frame, unlike some apos I’ve tested lately whose rotator mechanisms can work loose and tip the camera.

The Camera Angle Adjuster has female M63 threads to accept either the included visual back or one of the optional field flatteners. All the lock knobs are large and easy to adjust with gloves on, a nice touch many scopes lack.

In short, the Géar 90 has all the quality and features one could wish for in a premium scope. However, its plain back and white finish isn’t as sexy as the carbon fiber tubes and colorfully anodized fittings of some of the competition.

Each Starfield Géar scope includes an inspection certificate documenting the optical performance of that unit as measured on a Zygo interferometer. Credit: Alan Dyer

Géar 90 for Visual Use

The test report for the unit I was loaned for review stated that its optics had a very low peak-to-valley wavefront error of 0.126 wave (0.25 wave, or 1/4 wave, is considered diffraction limited). The Strehl Ratio was given as a very high 0.987, with 1.0 being theoretical perfection.

While I can’t verify the numbers, I think they were accurate in that, under a critical high-power star test, stars showed textbook perfect diffraction patterns. There was no sign of astigmatism and the barest level of spherical aberration that made extra-focal patterns not quite identical.

Bright stars like Vega and Altair exhibited a clean and tight central Airy disk and a well-defined first diffraction ring. The double-double star Epsilon Lyrae appeared like four clean drops of white paint on black with ample black sky separating the close stars.

But most impressive is that the Géar 90 showed no false color, whether in focus or when racking inside and outside of focus, even on demanding targets such as Vega and Jupiter. Jupiter exhibited excellent fine detail in its cloud belts.

The objective is superbly multicoated. The tube interior is well-blackened and fitted with two knife-edge baffles, to suppress stray light and lens flares. Credit: Alan Dyer

The FPL53 element in the triplet main lens, made of top grade Japanese Ohara glass, was doing its job. Lower cost triplet apos with lesser grades of glass, while sharp, can still exhibit cyan- and magenta-tinted images either side of focus and some residual blue chromatic aberration in-focus.

While the lens cell has collimation adjustments, I had no reason to touch them. The optical performance was equal to the best I have tested from the prestige brands of refractors. I think it will please even the most discerning apo aficionados.

This portrait of the Pacman Nebula is a stack of multiple 8- and 4-minute exposures, both with and without a narrowband filter, with the Géar 90 and 0.8x Adjustable Reducer. Credit: Alan Dyer

Géar 90 for Photography

As expected, I saw no evidence of longitudinal chromatic aberration in long-exposure images of starfields, again unlike lesser apos that can leave blue halos on many stars.

It is only when using the 0.8x reducer that some lateral chromatic aberration was visible off-axis, adding small blue tails to the stars in the very corners of the frame.

The knurled ring on the optional Reducer can be turned to move the Reducer in and out over a range of 12 mm. The spacing scale is indicated by the arrow. Credit: Alan Dyer

As with most refractors, deep-sky imaging with the Géar scopes requires a field flattener. I tested the Géar 90 with Starfield’s 0.8x Adjustable Reducer, which flattens the field and speeds up the scope to f/4.8 yielding a field of 4.7° by 3.1° on a full-frame sensor. Starfield also offers a 1.0x Flattener, but I did not test one. I prefer speed over focal length.

With the 0.8x reducer, stars were very nearly pinpoint to the corners, showing just a small degree of elongation from coma or astigmatism (or likely a mixture of both) at the extreme corners. Though not perfect, this is field flatness as good as or better than I have seen on many apo-flattener combinations.

This frame from the Pacman set shows the full height of the central area of a full-frame image, along with 300% blow-ups of each corner to show aberrations at the extreme corners. Credit: Alan Dyer

The reducer I tested allows adjusting the reducer-to-sensor spacing, a handy feature that should do away with fussing with thin spacers and shims to achieve precise spacing. For my tests, I used it at the spacing of 2.6 mm recommended for DSLRs. Using it at an even shorter spacing made off-axis images worse, but setting it to longer 3 mm and 4 mm spacings didn’t seem to make much difference. However, users should run their own tests to see what works best with their setup.

This exposure of Vega was taken in deep twilight. Contrast is boosted to demonstrate the level of vignetting with the Adjustable Reducer and the lack of chromatic aberration on-axis. Credit: Alan Dyer

Vignetting, an inevitable drawback to using reducers, was well-controlled, with the corners darkening about 0.8 of an f-stop compared to the frame center. This is a mild and gradual level of vignetting easily correctable in calibration or processing.

In all, I was very impressed with the photos from the Géar 90, so much so I soon started using it for my own “keeper” images. That’s a testament to how good a scope is in my book.

The Géar 90 comes in a sturdy footlocker case. However, there’s no room for visual accessories or the photographic field flattener, shown here in front. Credit: Alan Dyer

Recommendations

If you are a refractor fan adamant that views should be free of any false color, then the Géar 90 will likely satisfy you without the cost and long wait times of more prestigious brands. For imaging, the Géar 90 offers all the solid fittings needed for a frustration-free experience in attaching, balancing, focusing, and framing a camera. Image quality across a full-frame sensor is superb, good enough to please all but the most pixel-peeping critic. And unlike some dedicated astrographs, the Géar 90 can also be used visually.

It is possible to find telescopes with similar specs and fittings sold elsewhere in the world, such as from First Light Optics in the U.K. (their StellaMira 90 ED), or Teleskop-Express in Germany (their CF-APO 90), or in the U.S. from Orion Telescopes (their new EON 90 ED). However, each of the other variants uses a different type of glass. In North America, Starfield Optics is the sole source for this telescope with Ohara FPL53 glass and a test certificate.

The Starfield Géar 90 will be a good match for a smaller equatorial mount like the Sky-Watcher EQM-35 shown here. Credit: Alan Dyer

Starfield sells direct or through its dealers, with OPT being the only U.S. dealer listed as of this writing.

When looking at Starfield’s website, keep in mind that prices are in Canadian dollars. As of this writing, the strong US dollar compared to Canadian funds makes the Géar 90 an even more attractive value for its premium performance for those in the US. Couple the Géar 90 with a moderately sized and priced mount and you have a powerful astrophoto package for beginners and experts alike for a reasonable cost.

 

Plus

Superbly sharp, color-free apo optics

Wide, flat field with optional 0.8x Reducer

Excellent fittings and finish

Priced in Canadian dollars! 

 

Minus

Residual off-axis aberrations with Reducer

Plain black-and-white finish

No room in included case for accessories

 

MSRP: $2,350 Canadian; Adjustable 0.8x Reducer $260 Canadian

Website: https://starfieldoptics.com/gear90-90mm-edt

 

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About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at www.amazingsky.com has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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