William Optics

William Optics FLT120 FluoroStar APO

No longer sold

William Optics' flagship 120mm FluoroStar triplet, an FPL-53 apo that pairs beautiful build with strong visual and imaging performance at a price well below the Japanese premium brands.

89/ 100

Polaris Score

#2 of 6 large triplet apo

See the breakdown ↓

Aperture

120mm

Focal Length

780mm

Focal Ratio

f/6.5

Mount Type

None (OTA only)

Optical Design

Triplet APO

Weight

5.5 kg

Try in simulator →

No longer sold

Discontinued by the manufacturer (per Agena Astro). We keep the page for reference — see current alternatives below.

See alternatives ↓

What it's built forOpen these in the simulator →

This telescope was built for sweeping wide.

A short, fast refractor with a generous true field — the whole sword of Orion in one view, star fields that spill past the field stop. It rewards low power and dark skies far more than chasing magnification.

Widest true fieldsTack-sharp to the edge

The view people remember

Andromeda, wider than the Moon.

A vast soft oval with a blazing core — two and a half million light-years of galaxy, spilling well past the field of view under a genuinely dark sky.

See Andromeda Galaxy through this telescope →

Where else it shines

Within reach

Orion Nebula

Stronger structure — embedded stars plus dark lanes within the core

Open view →

Easy first target

The Pleiades

Rich field — fainter members fill out the cluster

Open view →

Rewards a dark sky

Whirlpool Galaxy

Definite galaxy shape — core stands out against the sky

Open view →

Also excellent on

Saturn

Recognizable disk with subtle markings under steady seeing

Open view →

✦

Tight planetary detail belongs to a longer scope. This one trades reach for a breathtaking field.

01What it's good at

What it's best at — and the trade-offs.

Best at

✓The FPL-53 air-spaced triplet controls color extremely well, so bright objects stay clean at high power

✓120mm at f/6.5 balances high-resolution visual work with a focal length that frames deep-sky targets for imaging

✓William Optics build quality, focuser and finish are a cut above at this price point

✓It scales from native visual use to flat, fast imaging with the matched flattener or reducer

Trade-offs

!The tube is heavy and needs a genuinely stable mount to steady it

!A matched flattener or reducer is a separate purchase for imaging

!It is an OTA only and needs a mount, diagonal and eyepieces

!It takes longer to cool than a smaller apo

02In plain English

What These Numbers Mean

Aperture

120 mm

Nearly five inches of apochromatic glass, enough for high-contrast planetary and lunar views and for deep-sky imaging that reaches genuinely faint detail. Unobstructed optics give it contrast a reflector of the same size cannot match.

Focal length

780 mm

A versatile middle length: 156x with a 5 mm eyepiece for planets, and enough field for larger nebulae on APS-C when imaging with a flattener.

Focal ratio

f/6.5

Moderately fast, so exposures stay practical while colour correction remains straightforward for a triplet. A good compromise for someone who both observes and images.

Optical design

FPL-53 triplet apochromat

Three elements with premium ED glass remove visible false colour, keeping bright stars white and lunar limbs clean. Triplets hold more glass than doublets, so allow time to reach outdoor temperature.

Weight

5.5 kg tube

About 12 lb bare, closer to 16 lb once rings, camera and guiding are attached. A mid-size equatorial in the 15 kg class handles it comfortably.

Mount

OTA only

You supply the mount. The tube's length matters as much as its mass here, so favour a mount with a solid tripod rather than one rated only just above the weight.

02The Polaris Score

How it scores, and why.

89/ 100

William Optics FLT120 FluoroStar APO

#2 of 6 large triplet apo

Performance

Ease of use

Portability

Upgrade potential

Polaris weighs optical capability, how easy the scope is to live with, how portable it is, and how far it takes you before you outgrow it — not list price or brand.

03Who it's for