telescopecomparison · 2-way
William Optics Ultra-Cat 56 vs SharpStar 61EDPH III
William Optics
Ultra-Cat 56
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
SharpStar
61EDPH III
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
-20% focal length
-8% aperture
Faster by 0.7 f-stops
Specifications
| Specification | William Optics Ultra-Cat 56 | SharpStar 61EDPH III |
|---|---|---|
| Optics | ||
| Type | refractor | Refractor |
| Optical design | Petzval (5-element advanced) | Doublet APO |
| Aperture | 56mm | 61mm |
| Focal length | 269mm | 335mm |
| Native f/ratio | f/4.8 | f/5.5 |
| Image circle | 50mm | 32mm |
| Full-frame support | Yes | No |
| Physical | ||
| Weight | 2.6kg | 2.4kg |
Advantages of William Optics Ultra-Cat 56
- Wider field — 269mm vs 335mm focal length
- Faster optics at f/4.8 vs f/5.5
- Larger image circle (50mm) — supports bigger sensors
Advantages of SharpStar 61EDPH III
- Tighter framing — 335mm vs 269mm focal length
Best for — William Optics Ultra-Cat 56
- Wide-field nebulae and Milky Way regions
- Fast imaging — short exposures per sub
- Full-frame astro cameras and DSLRs
Best for — SharpStar 61EDPH III
- Wide-field nebulae and Milky Way regions
William Optics Ultra-Cat 56 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 7.67° × 5.11°Scale: 2.88"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 5.01° × 3.34°Scale: 2.88"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 2.41° × 2.41°Scale: 2.88"/px
SharpStar 61EDPH III — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 6.16° × 4.11°Scale: 2.32"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 4.02° × 2.69°Scale: 2.32"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.93° × 1.93°Scale: 2.32"/px
William Optics Ultra-Cat 56 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
SharpStar 61EDPH III — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
