telescopecomparison · 2-way
Celestron RASA 8 vs William Optics RedCat 91 WIFD
Celestron
RASA 8
Best suited for beginners and wide-field enthusiasts running a backyard imaging setup.
William Optics
RedCat 91 WIFD
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
Key differences
-11% focal length
+123% aperture
Faster by 2.9 f-stops
Specifications
| Specification | Celestron RASA 8 | William Optics RedCat 91 WIFD |
|---|---|---|
| Optics | ||
| Type | SCT | refractor |
| Optical design | Rowe-Ackermann Schmidt | Petzval (5-element advanced) |
| Aperture | 203mm | 91mm |
| Focal length | 400mm | 448mm |
| Native f/ratio | f/2.0 | f/4.9 |
| Image circle | 32mm | 55mm |
| Full-frame support | No | Yes |
| Physical | ||
| Weight | 7.7kg | 4.7kg |
Advantages of Celestron RASA 8
- Wider field — 400mm vs 448mm focal length
- 123% more light-gathering aperture
- Faster optics at f/2 vs f/4.9
Advantages of William Optics RedCat 91 WIFD
- Tighter framing — 448mm vs 400mm focal length
- Larger image circle (55mm) — supports bigger sensors
- Lighter (4.72kg vs 7.7kg) — easier to travel with
Best for — Celestron RASA 8
- Large emission nebulae and star clusters
- Fast imaging — short exposures per sub
- Faint-object imaging under dark skies
Best for — William Optics RedCat 91 WIFD
- Large emission nebulae and star clusters
- Fast imaging — short exposures per sub
- Full-frame astro cameras and DSLRs
Celestron RASA 8 — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 5.16° × 3.44°Scale: 1.94"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.37° × 2.25°Scale: 1.94"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.62° × 1.62°Scale: 1.94"/px
William Optics RedCat 91 WIFD — typical FOV & scale
- With Full-frame (36×24mm, 3.76µm)FOV: 4.60° × 3.07°Scale: 1.73"/px
- With APS-C (23.5×15.7mm, 3.76µm)FOV: 3.01° × 2.01°Scale: 1.73"/px
- With IMX533 square (11.3×11.3mm, 3.76µm)FOV: 1.45° × 1.45°Scale: 1.73"/px
Celestron RASA 8 — recommended user
Best suited for beginners and wide-field enthusiasts running a backyard imaging setup.
William Optics RedCat 91 WIFD — recommended user
Best suited for beginners and wide-field enthusiasts running a portable travel rig.
