telescopecomparison · 2-way
William Optics Ultra-Cat 131 vs Askar FRA600
William Optics
Ultra-Cat 131
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Askar
FRA600
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Key differences
+8% focal length
+21% aperture
Faster by 0.7 f-stops
Specifications
| Specification | William Optics Ultra-Cat 131 | Askar FRA600 |
|---|---|---|
| Optics | ||
| Type | refractor | Refractor |
| Optical design | Petzval (5-element advanced) | Petzval Quintuplet APO |
| Aperture | 131mm | 108mm |
| Focal length | 648mm | 600mm |
| Native f/ratio | f/4.9 | f/5.6 |
| Image circle | 60mm | 60mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 11.3kg | 7.8kg |
Advantages of William Optics Ultra-Cat 131
- 21% more light-gathering aperture
- Faster optics at f/4.9 vs f/5.6
Advantages of Askar FRA600
- Lighter (7.8kg vs 11.3kg) — easier to travel with
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
Best for — Askar FRA600
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
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
Askar FRA600 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 3.44° × 2.29°Scale: 1.29"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.24° × 1.50°Scale: 1.29"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.08° × 1.08°Scale: 1.29"/px
William Optics Ultra-Cat 131 — recommended user
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
Askar FRA600 — recommended user
Best suited for intermediate imagers building a versatile kit running a backyard imaging setup.
