telescopecomparison · 2-way
William Optics FLT 156 vs William Optics GT 81
William Optics
FLT 156
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
William Optics
GT 81
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+127% focal length
+93% aperture
Slower by 1.1 f-stops
Specifications
| Specification | William Optics FLT 156 | William Optics GT 81 |
|---|---|---|
| Optics | ||
| Type | refractor | refractor |
| Optical design | Apo triplet FPL-53 | Apo triplet FPL-53 |
| Aperture | 156mm | 81mm |
| Focal length | 1085mm | 478mm |
| Native f/ratio | f/7.0 | f/5.9 |
| Image circle | 52mm | 44mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 11.5kg | 3.8kg |
Advantages of William Optics FLT 156
- Tighter framing — 1085mm vs 478mm focal length
- 93% more light-gathering aperture
- Larger image circle (52mm) — supports bigger sensors
Advantages of William Optics GT 81
- Wider field — 478mm vs 1085mm focal length
- Faster optics at f/5.9 vs f/7
- Lighter (3.8kg vs 11.5kg) — easier to travel with
Best for — William Optics FLT 156
- Medium-sized galaxies and planetary nebulae
- Full-frame astro cameras and DSLRs
Best for — William Optics GT 81
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
William Optics FLT 156 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 1.90° × 1.27°Scale: 0.71"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 1.24° × 0.83°Scale: 0.71"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 0.60° × 0.60°Scale: 0.71"/px
William Optics GT 81 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.32° × 2.88°Scale: 1.62"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.82° × 1.88°Scale: 1.62"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.35° × 1.35°Scale: 1.62"/px
William Optics FLT 156 — recommended user
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
William Optics GT 81 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.