Thanks! So are you satisfied with it?
The scope side thread might be an issue, there is only M102, M88 and M68 available (see here), so I'd need a special adapter. The exit side of the Riccardi seems to be M68x1 female, so I should be able to use the original adapters of the telescope from there on (i.e., 'replacing' the M88→M68 step with the flattener).
I'm using the larger Ricardi diameter. I think they make a slightly smaller diameter also. The larger one comes in two versions (in 1X), basically the same but designed for longer fl and shorter fl with an overlapping range at about F-7 plus or minus. Inquire about the thread size on the 4 inch focuser directly to TS for exact details on the focuser threads for best information, specifically ask about the fitment of the Ricardi flattener. Also Markus ludes at APM has some back focus charts with spacing for the Ricardi flatteners (to a large variety of different telescopes) . The Ricardi 's are first class quality. The larger diameter version will provide a flat field to cover all of a full frame sensor. APM will make special back focus spacers that thread onto the Ricardi - you may have to specify the optical train as having a specific camera imager setback sensor and if using any devices are in between such as filter slider or wheel and OAG device.
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