telescopecomparison · 2-way
William Optics GT 81 vs Sky-Watcher Evostar 72ED
William Optics
GT 81
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Sky-Watcher
Evostar 72ED
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+14% focal length
+13% aperture
Specifications
| Specification | William Optics GT 81 | Sky-Watcher Evostar 72ED |
|---|---|---|
| Optics | ||
| Type | refractor | refractor |
| Optical design | Apo triplet FPL-53 | Apo doublet FPL-53 |
| Aperture | 81mm | 72mm |
| Focal length | 478mm | 420mm |
| Native f/ratio | f/5.9 | f/5.8 |
| Image circle | 44mm | 44mm |
| Full-frame support | Yes | No |
| Physical | ||
| Weight | 3.8kg | 2.4kg |
Advantages of William Optics GT 81
- Tighter framing — 478mm vs 420mm focal length
- 13% more light-gathering aperture
Advantages of Sky-Watcher Evostar 72ED
- Wider field — 420mm vs 478mm focal length
- Lighter (2.4kg vs 3.8kg) — easier to travel with
Best for — William Optics GT 81
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — Sky-Watcher Evostar 72ED
- Large emission nebulae and star clusters
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
Sky-Watcher Evostar 72ED — 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
William Optics GT 81 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Sky-Watcher Evostar 72ED — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.