telescopecomparison · 2-way
William Optics Ultra-Cat 76 vs William Optics Zenithstar 61 II
William Optics
Ultra-Cat 76
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
William Optics
Zenithstar 61 II
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+25% aperture
Faster by 1.1 f-stops
Specifications
| Specification | William Optics Ultra-Cat 76 | William Optics Zenithstar 61 II |
|---|---|---|
| Optics | ||
| Type | refractor | refractor |
| Optical design | Petzval (5-element advanced) | Apo doublet FPL-53 |
| Aperture | 76mm | 61mm |
| Focal length | 365mm | 360mm |
| Native f/ratio | f/4.8 | f/5.9 |
| Image circle | 50mm | 44mm |
| Full-frame support | Yes | No |
| Physical | ||
| Weight | 3.8kg | 1.9kg |
Advantages of William Optics Ultra-Cat 76
- 25% more light-gathering aperture
- Faster optics at f/4.8 vs f/5.9
- Larger image circle (50mm) — supports bigger sensors
Advantages of William Optics Zenithstar 61 II
- Lighter (1.9kg vs 3.81kg) — easier to travel with
Best for — William Optics Ultra-Cat 76
- Large emission nebulae and star clusters
- Fast imaging — short exposures per sub
- Full-frame astro cameras and DSLRs
Best for — William Optics Zenithstar 61 II
- Large emission nebulae and star clusters
William Optics Ultra-Cat 76 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 5.65° × 3.77°Scale: 2.12"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.69° × 2.46°Scale: 2.12"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.77° × 1.77°Scale: 2.12"/px
William Optics Zenithstar 61 II — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 5.73° × 3.82°Scale: 2.15"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.74° × 2.50°Scale: 2.15"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.80° × 1.80°Scale: 2.15"/px
William Optics Ultra-Cat 76 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
William Optics Zenithstar 61 II — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
