After owning this scope for quite a few years now, I wanted to share my thoughts and give a short overview of this 3" Japanese astro-imaging icon.
Overview
The FSQ-85EDX is an elegantly crafted, premium, lightweight Japanese-made apochromatic refractor, ideal for wide-field imaging. It is the smaller sibling to the larger and equally acclaimed FSQ-106EDX.
Although it has been around for quite a long time now, the FSQ-85 still maintains its status as being one of, if not the best 3" imaging refractor money can buy.
The FSQ-85 was introduced to bring quite a few improvements over Takahashi's earlier FCT-76 Fluorite Triplet Apochromatic Refractor. These include a modified Petzval Quadruplet optical design, featuring a field-flattener built into the optical tube. This provides an almost homogenous flat field spanning an image circle of 44mm, perfect for use with large sensor CCD and CMOS cameras.
It's shorter optical tube assembly, in addition to making the scope more compact and easier to store, results in a faster F/5.3 design over the FCT-76's F/6.4 focal ratio. This also makes the FSQ-85 better for visual use, as one of the problems with the FCT-76's longer optical tube, was that 2" eyepieces could not focus without the use of optional visual adapters. The FCT-76 was designed with 1.25" eyepieces in mind; a classic characteristic of earlier Tak scopes. The FSQ-85's shorter OTA and generous back focus allow it to be used out of the box with 2" eyepieces. This makes it ideal for use in a binoviewer configuration.
Another issue with the FCT-76 was that it had a shorter dew shield than the FSQ-85 which allowed more stray light in from unwanted sources and was not as effective at dew protection.
The FSQ-85EDX features an oversided rack-and-pinion focuser like the larger FSQ-106EDX, allowing a large range of imaging equipment to be used with the scope. Unlike the FSQ-106EDX however, the focuser cannot be rotated and is fixed. It instead features a Camera Angle Adjuster (CAA), which allows eyepieces and cameras to be rotated to the optimal angle. The focuser also has two focus wheels; including a coarse adjustment and a smaller 1:7 ratio microfocuser for fine adjustment. This comes in handy for attaching focus motors for imaging.
The optical tube assembly is beautifully finished in classic Takahashi cream white and you can tell just by looking at it, that a lot of care and attention has gone into its design and assembly. At just under 4kg, it will also suit a large range of mounts, including compact models like the EQ-5 or if you can afford it, Takahashi's own EM-11 mount. This makes it easy to transport in the car to dark site locations, should you wish to. It is also light enough that you can piggyback it on another larger scope, such as a RC or larger refractor without any issues with balance. In my own setup, I piggyback it on a larger Altair 115EDT Triplet Apo that I use for narrower FOV imaging of smaller objects like galaxies and globular clusters etc.
The FSQ-85EDX can be purchased in an OTA only configuration or with the optional accessories, including the TKA00551 6x30 Finder, TKA00562 Finder Bracket and TKA21420S Tube Holder with Offset Plate (95mm). Although the TKA21420S Tube Holder is well made and robust, I opted for PrimaLuceLab's 95mm PLUS Support Rings instead, paired with their Losmandy style PLUS Dovetail Plates. I think the system's red finish suits the scope well and provides a more stable platform.
In terms of optical performance, the FSQ-85EDX is second to none. The use of extra-low dispersion glass (ED) provides razor-sharp, high contrast images with pinpoint stars; like diamonds on velvet, as you'd expect at this price point. I have found it effortless in allowing me to produce stunning astro images with no chromatic aberration visible around any stars. With a native focal length of 450mm and flat-field covering 5.6 degrees of the sky, the FSQ-85EDX can cover a lot of the larger objects in the sky with ease. When paired with the optional 0.73x QE Reducer, this allows for even more versatility.
At prime focus, at the edge of field (22mm from the optical axis) stars remain pinpoints, including on pixels of 7µ width.
One recent improvement made to the FSQ-85EDX was the inclusion of the 1.01x EDP Flattener. This is now included as standard with the scope and was introduced to correct for mild field curvature and edge of field astigmatism that is visible when using modern large format, ultra-small pixel sensors with the original telescope. It is stated to provide the same level of sharpness as provided by the FSQ-106EDX. I haven't tried the flattener myself, so can't comment on its performance and there have been reported cases by other users that there can still be some issues with stars in the image when paired with small pixel sensors.
Specifications
Price: £3,098 (OTA only) / £3,501 (with accessory package bundle)
Optical design: Petzval Quadruplet with ED glass (2 x S-FPL53 ED lenses)
Aperture: 85mm (3.3")
Focal length: 450mm (prime focus) / 455mm (with x1.01 Flattener)
Focal ratio: F/5.3 (prime focus) / F/5.4 (with x1.01 Flattener)
Imaging circle: 44mm
Optical tube length: 623mm (535mm with dew shield retracted)
Diameter of optical tube: 95mm
Diameter of dew shield: 114mm
Weight: 3.6kg
Focuser: rack-and-pinion with 1:7 microfocuser
Optional Accessories
In addition to the 1.01x Flattener, Takahashi offer a range of other accessories for use with the FSQ-85EDX for different applications; including the TKA36580 0.73x QE Reducer:
It also provides a 44mm corrected field but reduces the effective focal length to 327mm and the focal ratio to F/3.8. Additionally, it increases the field-of-view to 7.0 degrees. This allows for faster imaging, whilst increasing the field-of-view, allowing larger objects to be viewed and imaged, turning it into a true astrograph. One thing to bear in mind however is that it has a back focus requirement of 72.2mm. So, you may need a custom adapter to obtain this with your equipment. I recommend checking out Precise Parts for this, as they design custom adapters for astronomy: www.preciseparts.com. The reducer attaches directly to the back of the CAA on the scope.
A x1.5 extender is also available. It features an extra-low dispersion (ED) glass element and increases the effective focal length to 680mm and focal ratio to F/8.0. This is useful for visual purposes and the 2" barrel fits a large range of eyepieces.
Summary
Pros:
Arguably the best 3" imaging apo you can buy.
Unsurpassed optical performance for imaging and visual use.
Uncompromised Japanese build quality.
Large range of accessories allowing for more versatility.
Lightweight and compact - can be used on a large range of mounts and easy to transport.
Cons:
Accessories are quite expensive.
Focuser does not rotate like on the FSQ-106EDX.
In some cases, small pixel, modern CMOS sensors have been reported to still cause star issues with paired with the FSQ-106EDX, even with the flattener.
Despite the few drawbacks, the FSQ-85EDX is perhaps the best imaging apo in its class and is just as good a scope for visual use, as it is for imaging. Although the accessories are quite expensive, they do offer great optical performance and versatility. With its ultra-high contrast, pinpoint sharp images and large flat field, free of chromatic aberration, nothing else comes close and it's a scope that you'll want to keep for the rest of your life and pass on to future generations.
If you are interested in purchasing the FSQ-85EDX, visit First Light Optics (FLO) for more information: www.firstlightoptics.com/takahashi-fsq-85-series-refractor-telescopes/takahashi-fsq-85edx-f5-3-quadruplet-petzval-apo-refractor.html.