telescopecomparison · 2-way
William Optics RedCat 51 vs Borg 55FL
William Optics
RedCat 51
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
-7% aperture
Slower by 0.4 f-stops
Specifications
| Specification | William Optics RedCat 51 | Borg 55FL |
|---|---|---|
| Optics | ||
| Type | Refractor | refractor |
| Optical design | Petzval APO | Apo doublet fluorite |
| Aperture | 51mm | 55mm |
| Focal length | 250mm | 250mm |
| Native f/ratio | f/4.9 | f/4.5 |
| Image circle | 45mm | — |
| Full-frame support | Yes | No |
| Physical | ||
| Weight | 1.6kg | 1.2kg |
Advantages of William Optics RedCat 51
- Larger image circle (45mm) — supports bigger sensors
Advantages of Borg 55FL
- Faster optics at f/4.5 vs f/4.9
- Lighter (1.2kg vs 1.6kg) — easier to travel with
Best for — William Optics RedCat 51
- Wide-field nebulae and Milky Way regions
- Fast imaging — short exposures per sub
- Full-frame astro cameras and DSLRs
Best for — Borg 55FL
- Wide-field nebulae and Milky Way regions
- Fast imaging — short exposures per sub
William Optics RedCat 51 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 8.25° × 5.50°Scale: 3.10"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 5.39° × 3.60°Scale: 3.10"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 2.59° × 2.59°Scale: 3.10"/px
Borg 55FL — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 8.25° × 5.50°Scale: 3.10"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 5.39° × 3.60°Scale: 3.10"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 2.59° × 2.59°Scale: 3.10"/px
William Optics RedCat 51 — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Borg 55FL — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.