telescopecomparison · 2-way
ZWO FF70 APO vs William Optics GT 71
William Optics
GT 71
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+17% focal length
Slower by 1.1 f-stops
Specifications
| Specification | ZWO FF70 APO | William Optics GT 71 |
|---|---|---|
| Optics | ||
| Type | refractor | refractor |
| Optical design | Apo quadruplet ED | Apo triplet FPL-53 |
| Aperture | 70mm | 71mm |
| Focal length | 490mm | 420mm |
| Native f/ratio | f/7.0 | f/5.9 |
| Image circle | 44mm | 44mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 2.5kg | 3.4kg |
Advantages of ZWO FF70 APO
- Tighter framing — 490mm vs 420mm focal length
- Lighter (2.5kg vs 3.4kg) — easier to travel with
Advantages of William Optics GT 71
- Wider field — 420mm vs 490mm focal length
- Faster optics at f/5.9 vs f/7
Best for — ZWO FF70 APO
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — William Optics GT 71
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
ZWO FF70 APO — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.21° × 2.81°Scale: 1.58"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.75° × 1.84°Scale: 1.58"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.32° × 1.32°Scale: 1.58"/px
William Optics GT 71 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.91° × 3.27°Scale: 1.85"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.21° × 2.14°Scale: 1.85"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.54° × 1.54°Scale: 1.85"/px
ZWO FF70 APO — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
William Optics GT 71 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
