The FSQ-85EDX is a more mobile version of the FSQ-406EDX4 for lovers of wide-field deep sky imaging.
Like its predecessor, it is based on an apochromatic Petzval quadruplet formula wincluding ED glass. With a focal length of 450 mm and a flat field covering 5.6 degrees over the sky, this refractor is ideal for photography. It is delivered with a 1.01X corrector to make the most of recent sensors with smaller and smaller pixels. The image circle is 44 mm.
The rack-and-pinion focuser is deliberately oversized to improve accuracy and efficiency. It is controlled by a double system of 1/7 ratio wheels and equipped with a CAA (Camera Angle Adjuster) for photographic framing. The retractable dew shield saves space.
A focal reducer is available as an option to transform the telescope into a true high-end 328 mm astronomical telephoto lens, open at 3.9, with a 7 degree field of view on the sky and a 40 mm image circle!
Specifications
| Optical specifications | |
| Objective | Petzval Quadruplet with ED glass |
| Lens cell | Highly air-spaced quadruplet. 4 lenses/4 groups. 2 x S-FPL53 ED lenses |
| Coatings | Hard multicoatings |
| Diameter | 85 mm |
| At prime focus | |
| Focal length | 450 mm |
| Focal ratio | F/5.3 |
| Metal Back Distance | 197.5 mm |
| With Field Flattener 1.01X | |
| Focal length | 455 mm |
| Focal ratio | F/5.4 |
| Image circle diameter | 44 mm |
| Metal back distance | 56.2 mm |
| With Focal Reducer RD-QE0.73X | |
| Focal length | 327 mm |
| Focal ratio | F/3.8 |
| Image circle diameter | 44 mm |
| Metal back distance | 72.2 mm |
| With Extender EX-ED1.5X | |
| Focal length | 680 mm |
| Focal ratio | F/8 |
| Image circle diameter | 44 mm |
| Metal back distance | 117.5 mm |
| Mechanical specifications | |
| Length of the optical tube | 623 mm (535 mm with retracted dew-shield) |
| Diameter of the optical tube | 95 mm |
| Weight | 3.6 kg |
| Mise au point | Rack-and-pinion with 1/7 microfocuser |
Spot diagrams
