In May 2021, I ordered TPO 12" f/4 Imaging Newtonian from Oceanside Photo & Telescope (OPT). This 12" telescope has a fast focal ratio of f/4. I also purchased a Sky-Watcher Quattro Coma Corrector to use with this telescope.
| TPO 12" f/4 Imaging Newtonian Astrograph | |
|---|---|
| Primary Mirror: | 305mm (12.0") |
| Secondary Mirror: | 102mm (4.01") |
| Central Obstruction: | 33% (diameter); 11% (area) |
| Focal Length: | 1220mm (48.03") |
| Focal Ratio: | f/4 |
| Focal Ratio: | f/4.1 - with Sky-Watcher Quattro Coma Corrector |
| Dawes Limit: | 0.38 arc seconds |
| Rayleigh Limit: | 0.46 arc seconds |
| Light Transmission: | 94% |
| Focuser Type: | 2-inch Crayford-style focuser, dual-speed (10:1) |
| Tube Assembly: | rolled steel, flat black interior |
| Tube Dimensions: | Length - 1156mm (45.5"); Outer Diameter - 360mm (14.25") |
| Weight: | 18.1 kg (40 lbs.) |
| Image Circle: | 50 mm (1.97") |
| Field of View (35mm): | 1.3 x 1.9 degrees @ f3.6 |
| Field of View (DX): | 0.8 x 1.2 degrees @ f3.6 |