APM Riccardi Reducer 0.75x corrector for APO refractor telescopes
Massimo Riccardi, well-known optical designer from Italy, has developed a 3-element 0.75x reducer/flattener for apochromatic refractor telescopes. The reducer reduces the focal length of the telescope by a quarter and corrects the image field. Turn your telescope into a fast astrograph!
Telescope connection and required back-focus:
The large Riccardi Reducer has a male M82 thread at the telescope side. Via this thread, the reducer can be attached to the focuser of the apochromat. However, a back focus of at least 210 mm is necessary in this case. With the optional Tilting Mechanism TSJM82 – adjustment flange, you can tilt the image field and further improve the sharpness at the edge.
If your apo is equipped with a 3.5″ FeatherTouch focuser, you can sink the reducer into the draw tube. Required for this is that the draw tube has a larger inner diameter than 90 mm. In this case, the required back focus distance is reduced to only 110 mm. For this adaption, you need the adapter FT35-Rired82. On request, we match the adapter individually to your camera system.
Working distance – back focus – from corrector to the camera sensor:
The working distance is calculated from the female M82x1 thread at the camera side. The thread is not taken into account, so the calculation starts from the edge of the reducer´s body. The distance depends on the focal length of the refractor. As a basic rule: the shorter the focal length, the longer the working distance.
♦ focal length < 650 mm: 80.7 mm
♦ focal length 660-700 mm: 80 mm
♦ focal length 710-780 mm: 77.4 mm
♦ focal length 790-800 mm: 76.5 mm
♦ focal length 810-1000 mm: 76 mm
♦ focal length > 1000 mm: 75 mm
Specific values were determined for the following telescopes:
♦ TS and APM APO 107/700 mm: 80 mm
♦ TS Photoline APO 115/800 mm: 76.50 mm
♦ TS Photoline APO 130/780 mm: 77.40 mm
♦ Skywatcher Esprit 152/1000 mm: 77 mm
The reducer can also be used for RC telescopes from 10″ upwards:
♦ GSO/TS/AstroTec RC from 10″ upwards: 76 mm