telescopecomparison · 2-way
William Optics RedCat 91 vs Askar SQA85
William Optics
RedCat 91
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+7% aperture
Faster by 0.3 f-stops
Specifications
| Specification | William Optics RedCat 91 | Askar SQA85 |
|---|---|---|
| Optics | ||
| Type | Refractor | refractor |
| Optical design | Petzval APO | Quadruplet astrograph FPL-51 |
| Aperture | 91mm | 85mm |
| Focal length | 496mm | 500mm |
| Native f/ratio | f/5.5 | f/5.8 |
| Image circle | 45mm | 52mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 4.3kg | 4.4kg |
Advantages of William Optics RedCat 91
- Faster optics at f/5.45 vs f/5.8
Advantages of Askar SQA85
- Larger image circle (52mm) — supports bigger sensors
Best for — William Optics RedCat 91
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — Askar SQA85
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
William Optics RedCat 91 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.16° × 2.77°Scale: 1.56"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.71° × 1.81°Scale: 1.56"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.31° × 1.31°Scale: 1.56"/px
Askar SQA85 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.13° × 2.75°Scale: 1.55"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.69° × 1.80°Scale: 1.55"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.29° × 1.29°Scale: 1.55"/px
William Optics RedCat 91 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Askar SQA85 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.