telescopecomparison · 2-way
William Optics RedCat 91 vs Takahashi FSQ-85EDX
William Optics
RedCat 91
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Takahashi
FSQ-85EDX
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
+10% focal length
+7% aperture
Specifications
| Specification | William Optics RedCat 91 | Takahashi FSQ-85EDX |
|---|---|---|
| Optics | ||
| Type | Refractor | Refractor |
| Optical design | Petzval APO | Petzval APO |
| Aperture | 91mm | 85mm |
| Focal length | 496mm | 450mm |
| Native f/ratio | f/5.5 | f/5.3 |
| Image circle | 45mm | 44mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 4.3kg | 4.0kg |
Advantages of William Optics RedCat 91
- Tighter framing — 496mm vs 450mm focal length
Advantages of Takahashi FSQ-85EDX
Closely matched on the compared specs.
Best for — William Optics RedCat 91
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — Takahashi FSQ-85EDX
- 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
Takahashi FSQ-85EDX — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.58° × 3.06°Scale: 1.72"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.99° × 2.00°Scale: 1.72"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.44° × 1.44°Scale: 1.72"/px
William Optics RedCat 91 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Takahashi FSQ-85EDX — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.