telescopecomparison · 2-way
William Optics FLT 91 vs Takahashi FSQ-85EDX
William Optics
FLT 91
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Takahashi
FSQ-85EDX
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+20% focal length
+7% aperture
Slower by 0.6 f-stops
Specifications
| Specification | William Optics FLT 91 | Takahashi FSQ-85EDX |
|---|---|---|
| Optics | ||
| Type | Refractor | Refractor |
| Optical design | Triplet APO | Petzval APO |
| Aperture | 91mm | 85mm |
| Focal length | 540mm | 450mm |
| Native f/ratio | f/5.9 | f/5.3 |
| Image circle | 44mm | 44mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 4.5kg | 4.0kg |
Advantages of William Optics FLT 91
- Tighter framing — 540mm vs 450mm focal length
Advantages of Takahashi FSQ-85EDX
- Wider field — 450mm vs 540mm focal length
- Faster optics at f/5.3 vs f/5.9
Best for — William Optics FLT 91
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — Takahashi FSQ-85EDX
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
William Optics FLT 91 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 3.82° × 2.55°Scale: 1.44"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.49° × 1.67°Scale: 1.44"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.20° × 1.20°Scale: 1.44"/px
Takahashi FSQ-85EDX — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.58° × 3.06°Scale: 1.72"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.99° × 2.00°Scale: 1.72"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.44° × 1.44°Scale: 1.72"/px
William Optics FLT 91 — recommended user
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Takahashi FSQ-85EDX — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.