Astronomy Specialist


$3,631.00 USD

William Optics

Apochromatic triplet

120 mm


710 mm

7.2 kg

Color: Gold


Coming soon! The new William Optics Fluorostar FLT 120 is a three element air-spaced apochromatic refractor with a focal ratio of f/6.5 and a focal length of 780mm. Utilizing FPL-53 synthetic fluorite glass with STM coatings, this telescope provides excellent aberration correction and amazing optical performance.

The 3.3" dual speed rack & pinion focuser is smooth, stable and reliable, providing no slippage over long imaging sessions. The super smooth field rotator includes markings for every degree, and a solid thumbscrew position lock.

The CNC-machined and anodized handle bar with finder-style saddle is perfect for attaching a guide scope or other accessories. The FLT 120 also includes William Optics' innovative clear Bahtinov mask integrated into the lens cap. The Rotolock 2 inch adapter provides for a solid and efficient connection for a William Optics 2 inch diagonal, and other accessories.

William Optics uses high quality steel lens cells for their Gran Turismo and FLT triplet refractors. This is perfect for temperature compensation and will prevent pinched optics in cold weather conditions.

For best imaging results, it is recommended to pair the FLT 120 with the Flat68III 1.0x field flattener or Flat7A 0.8x reducer.

Note: As the Flat6AIII / Flat7A an adjustable flattener, you must adjust the distance for your specific telescope. See the Instructions tab above.
FLUOROSTAR 120 F/6.5 APO TRIPLET & Flat68III spot diagram FLUOROSTAR 120 F/6.5 APO TRIPLET & Flat68III longitudinal aberration FLUOROSTAR 120 F/6.5 APO TRIPLET & Flat6AIII spot diagram FLUOROSTAR 120 F/6.5 APO TRIPLET & Flat6AIII longitudinal aberration FLUOROSTAR 120 F/6.5 APO TRIPLET Zygo test report


Optical design

Air-spaced apochromatic triplet

Objective diameter

120 mm

Focal length

780 mm

Focal ratio


Image circle

44.4 mm (with field flattener)

Compatible flattener

William Optics Flat68III, Flat7A

Mount attachment

Losmandy-style dovetail bar


Rack & pinion dual speed 3.3" diameter

Camera connection

M92 x 1, 2" Rotolock


65.2 mm (with Flat68III)

Tube weight

7.2 kg

Tube length

680 mm (retracted), 850 mm (extended) 

Tube diameter


Dew shield diameter



WO-A-F120GD-RP33 (Gold), WO-A-F120RD-RP33 (Red)



  • Fluorostar 120
  • Lens cap with Bahtinov mask
  • Finder saddle handle bar
  • Losmandy-style dovetail bar
  • Soft carry case


Note: Once you have unscrewed the rear adapter to the appropriate value in the table below, the remaining backfocus distance to make up will be 55mm from the rear M48 thread.  

Distance adjustment needed for correct backfocus with Flat6AIII 0.8x reducer

FLT91 5.4 mm
FLT120 10.7 mm

Customer Reviews

Based on 2 reviews
Martin Williams

FLUOROSTAR 120 F/6.5 APO TRIPLET William Optics quality refractor optics are very sharp and a top quality focuser very happy with the refractor not to heavy for my losmandy G11 mount
I have looked at the planets Jupiter and Saturn 150 x could easily see the band clouds on Jupiter and the rings around Satern easily seen very sharp and clear using this refractor mostly for imaging i have taken NGC2070 Narrow Band which i will post on here. the refractor is top notch for Astrophotography taken with x0.8 Flattener 7. Perth Hills.
Martin Williams

John Holgate

Out of the box, or 'soft' case, the Fluorostar 120 is a very impressive bit of kit. Tube rings and dovetail are beautifully machined with all sorts of accessory attachment points. Loosen the knobs a little on the tube rings and the scope slides smoothly to adjust balance. The finish on the scope is a lovely matt pearl white - not sure if it's powder coated, but it's a huge step up from the usual Chinese ED scopes. The long dew cap slides smoothly out and can be locked in place with a nylon tipped screw. If I was really, really picky, I could say that the dew cap does droop just a mm or two when fully extended - but that's nitpicking. Focusser is very, very impressive with the rotolock, 90mm of travel and the ability to rotate either the whole focus unit including the knobs, or just the draw tube. Either rotate smoothly with no play - ideal for adjusting either camera angle or diagonal position. The fine focus also works very nicely. Travel is smooth although not completely uniform in tension on my scope - again, I'm being very picky as it does not affect the focusing at all. I've only been photographing with a DSLR and the focusser has been holding that without problem or effort. In the past I have found EQ mounts to be an absolute PITA for visual, but having the ability to easily rotate either the draw tube or the entire focusser has taken the pain out of it.

First light was late afternoon after I had put it on the AZEQ6 and aimed it out the observatory door at a distant transmitter mast. I was surprised at how neutral, flat and free of fringing it was, so much so that I immediately grabbed the 7mm Delite and had without doubt the cleanest daytime view I'd ever seen. The atmosphere must have been very steady at that time. Venus was the first night time target, and with the 7mm, the best view of Venus I've seen. Just the barest hint of yellow on the edge - and I can't say that wasn't my glasses or eyepiece. No color at all on Jupiter's outline or the edge of the Moon. Nor have I seen any CA in the photos I've taken with the DSLR.

I have been suitably impressed with the optics both visually and for AP. I was hoping that a nice Apo Triplet would give me a nice color-free image and not show signs of falling apart under 100-plus magnification. The 120mm is actually better than I'd hoped it would be - just when I think, nah, this will be too much power for the current seeing, it surprises me by wanting a little more. Star images are tight, pinpoints with uniform and perfectly circular airy discs - not identical either side of focus, but from my understanding, they are very good.

The 2" ES 34mm (68) gave a much more impressive and flatter view than I was expecting - another 'wow' moment. As was an older 9mm Vixen lanthium eyepiece when I popped that in for a look at Jupiter - best I've ever seen through it.

It's very compact for a 120mm with the focus racked in and dewshield retracted. It feels very solid and relatively heavy for its size. With a small guide scope and red dot finder, my two 5kg weights are around an inch from the end of the counterweight bar. The case is well padded and compact and should be excellent for transporting to the occasional star party.

In the flesh, this scope did not disappoint and looking through it, is even better than looking at it! I'm looking forward to many dark nights spent with it.

The photo of M42 is 5 x 30 second un-guided exposures under a full moon. Comet Leonard was photographed in a twilight sky (30s exposures) and Tuc 47 also under a full moon.



From $3,631.00 USD



  • OTA Only
  • With 0.8x Reducer
  • With 1x Flattener

Optical design

Apochromatic triplet

Image circle

Focal ratio



120 mm

Focal length

710 mm

Optical thickness



Colour or Mono

Pixel size

Sensor dimensions


Sensor diagonal

Quantum efficiency

Read noise

Fullwell capacity

Bit depth


Camera backfocus

Filter size

Filter size

Bandpass (FWHM)

Bandpass (FWHM)

Glass thickness

Mount type

Payload capacity

Latitude range

Dovetail saddle

Slew speed


Periodic error correction

Counterweight shaft

Azimuth adjustment range

Internal diameter

Illuminated diameter

Compatible telescope external diameter


7.2 kg




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