telescopecomparison · 2-way
Celestron RASA 6 vs William Optics Ultra-Cat 76
William Optics
Ultra-Cat 76
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
-8% focal length
+100% aperture
Faster by 2.6 f-stops
Specifications
| Specification | Celestron RASA 6 | William Optics Ultra-Cat 76 |
|---|---|---|
| Optics | ||
| Type | astrograph | refractor |
| Optical design | Rowe-Ackermann Schmidt Astrograph | Petzval (5-element advanced) |
| Aperture | 152mm | 76mm |
| Focal length | 335mm | 365mm |
| Native f/ratio | f/2.2 | f/4.8 |
| Image circle | 16mm | 50mm |
| Full-frame support | No | Yes |
| Physical | ||
| Weight | 3.8kg | 3.8kg |
Advantages of Celestron RASA 6
- 100% more light-gathering aperture
- Faster optics at f/2.2 vs f/4.8
Advantages of William Optics Ultra-Cat 76
- Larger image circle (50mm) — supports bigger sensors
Best for — Celestron RASA 6
- Wide-field nebulae and Milky Way regions
- Fast imaging — short exposures per sub
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
Celestron RASA 6 — 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 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
Celestron RASA 6 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
William Optics Ultra-Cat 76 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
