| Takahashi Corrected Cassigrain Astrograph: CCA-250 | |
|---|---|
| Optical design | Modified Cassegrain |
| Primary mirror diameter | 260mm (Useful aperture : 250mm) |
| Primary mirror features | 260mm, Pyrex parabolical mirror, F/2.75 |
| Secondary mirror features | 125mm diameter, Pyrex spherical mirror |
| Mirror coatings | Protected high reflectivity |
| Obstruction | 0.58 |
| Corrector | 3 lenses, 80mm diameter |
| Lens coatings | Fully multicoated |
| Back focus (BFL) | 193.9mm (without CAA) 155.4mm (with CAA) |
| Resolving power | 0.46" |
| Limiting magnitude (visual) | 13.8 |
| Light grasp | 1276x |
| Focal length | 1250mm |
| Focal ratio | F/5 |
| Image circle | 88mm, champ 4° (60% without vignetting) |
| Resolution | 2µ RMS (optical axis) 3µ RMS (10mm) 3µ RMS (20mm) 4µ RMS (30mm) 6µ RMS (40mm) |
| Tube length | 870mm |
| Tube diameter | 306mm |
| Materials | Aluminium and carbon fiber |
| Tube Weight | 22.8kg |
| Finder scope 尋星鏡 | 7x50 6.3° |