- Telescope focal length up to 350 mm: 70 mm
- Telescope focal length up to 420 mm: 65 mm
- Telescope focal length 450-500 mm: 61 mm
- Telescope focal length 510-600 mm: 58 mm
- Telescope focal length 610-700 mm: 57 mm
- Telescope focal length 710-790 mm: 56 mm
- Telescope focal length more than 800 mm: 55 mm