telescopecomparison · 2-way
William Optics FLT 91 vs Askar 65PHQ
William Optics
FLT 91
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Key differences
+30% focal length
+40% aperture
Faster by 0.5 f-stops
Specifications
| Specification | William Optics FLT 91 | Askar 65PHQ |
|---|---|---|
| Optics | ||
| Type | Refractor | Refractor |
| Optical design | Triplet APO | Quintuplet Petzval |
| Aperture | 91mm | 65mm |
| Focal length | 540mm | 416mm |
| Native f/ratio | f/5.9 | f/6.4 |
| Image circle | 44mm | 44mm |
| Full-frame support | Yes | Yes |
| Physical | ||
| Weight | 4.5kg | 3.6kg |
Advantages of William Optics FLT 91
- Tighter framing — 540mm vs 416mm focal length
- 40% more light-gathering aperture
- Faster optics at f/5.9 vs f/6.4
Advantages of Askar 65PHQ
- Wider field — 416mm vs 540mm focal length
- Lighter (3.6kg vs 4.5kg) — easier to travel with
Best for — William Optics FLT 91
- Large emission nebulae and star clusters
- Full-frame astro cameras and DSLRs
Best for — Askar 65PHQ
- 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 65PHQ — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.96° × 3.31°Scale: 1.86"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.24° × 2.16°Scale: 1.86"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.56° × 1.56°Scale: 1.86"/px
William Optics FLT 91 — recommended user
Best suited for intermediate imagers building a versatile kit running a portable travel rig.
Askar 65PHQ — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.