telescopecomparison · 2-way
William Optics FLT 91 vs Askar SQA85
William Optics
FLT 91
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Key differences
+8% focal length
+7% aperture
Specifications
| Specification | William Optics FLT 91 | Askar SQA85 |
|---|---|---|
| Optics | ||
| Type | Refractor | refractor |
| Optical design | Triplet APO | Quadruplet astrograph FPL-51 |
| Aperture | 91mm | 85mm |
| Focal length | 540mm | 500mm |
| Native f/ratio | f/5.9 | f/5.8 |
| Image circle | 44mm | 52mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 4.5kg | 4.4kg |
Advantages of William Optics FLT 91
Closely matched on the compared specs.
Advantages of Askar SQA85
- Larger image circle (52mm) — supports bigger sensors
Best for — William Optics FLT 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 FLT 91 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 3.82° × 2.55°Scale: 1.44"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 2.49° × 1.67°Scale: 1.44"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.20° × 1.20°Scale: 1.44"/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 FLT 91 — recommended user
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Askar SQA85 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.