telescopecomparison · 2-way
Celestron RASA 11 vs William Optics Ultra-Cat 131
Celestron
RASA 11
Best suited for intermediate imagers building a versatile kit running a permanent observatory setup.
William Optics
Ultra-Cat 131
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Key differences
+113% aperture
Faster by 2.7 f-stops
Specifications
| Specification | Celestron RASA 11 | William Optics Ultra-Cat 131 |
|---|---|---|
| Optics | ||
| Type | astrograph | refractor |
| Optical design | Rowe-Ackermann Schmidt Astrograph | Petzval (5-element advanced) |
| Aperture | 279mm | 131mm |
| Focal length | 620mm | 648mm |
| Native f/ratio | f/2.2 | f/4.9 |
| Image circle | 43mm | 60mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 20.0kg | 11.3kg |
Advantages of Celestron RASA 11
- 113% more light-gathering aperture
- Faster optics at f/2.22 vs f/4.9
Advantages of William Optics Ultra-Cat 131
- Larger image circle (60mm) — supports bigger sensors
- Lighter (11.3kg vs 20kg) — easier to travel with
Best for — Celestron RASA 11
- Large emission nebulae and star clusters
- Fast imaging — short exposures per sub
- Faint-object imaging under dark skies
- Full-frame astro cameras and DSLRs
Best for — William Optics Ultra-Cat 131
- Large emission nebulae and star clusters
- Fast imaging — short exposures per sub
- Full-frame astro cameras and DSLRs
Celestron RASA 11 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 3.33° × 2.22°Scale: 1.25"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.17° × 1.45°Scale: 1.25"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.04° × 1.04°Scale: 1.25"/px
William Optics Ultra-Cat 131 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 3.18° × 2.12°Scale: 1.20"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.08° × 1.39°Scale: 1.20"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.00° × 1.00°Scale: 1.20"/px
Celestron RASA 11 — recommended user
Best suited for intermediate imagers building a versatile kit running a permanent observatory setup.
William Optics Ultra-Cat 131 — recommended user
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
