telescopecomparison · 2-way
William Optics FLT 120 vs Borg 90FL
William Optics
FLT 120
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Key differences
+56% focal length
+33% aperture
Slower by 0.9 f-stops
Specifications
| Specification | William Optics FLT 120 | Borg 90FL |
|---|---|---|
| Optics | ||
| Type | Refractor | refractor |
| Optical design | Triplet APO | Apo doublet fluorite |
| Aperture | 120mm | 90mm |
| Focal length | 780mm | 500mm |
| Native f/ratio | f/6.5 | f/5.6 |
| Image circle | 44mm | — |
| Full-frame support | Yes | No |
| Physical | ||
| Weight | 7.7kg | 2.5kg |
Advantages of William Optics FLT 120
- Tighter framing — 780mm vs 500mm focal length
- 33% more light-gathering aperture
- Larger image circle (44mm) — supports bigger sensors
Advantages of Borg 90FL
- Wider field — 500mm vs 780mm focal length
- Faster optics at f/5.6 vs f/6.5
- Lighter (2.5kg vs 7.7kg) — easier to travel with
Best for — William Optics FLT 120
- Medium-sized galaxies and planetary nebulae
- Full-frame astro cameras and DSLRs
Best for — Borg 90FL
- Large emission nebulae and star clusters
William Optics FLT 120 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 2.64° × 1.76°Scale: 0.99"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 1.73° × 1.15°Scale: 0.99"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 0.83° × 0.83°Scale: 0.99"/px
Borg 90FL — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.13° × 2.75°Scale: 1.55"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.69° × 1.80°Scale: 1.55"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.29° × 1.29°Scale: 1.55"/px
William Optics FLT 120 — recommended user
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Borg 90FL — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.