Guiding MN190

[Gina]

I'm not 100% sure but I would imagine that with a focal reducer and field flattener, the field will only be flat if the distance from the FR/FF to the sensor is what it was designed to be. I would expect the amount of focal reduction to be dependent on spacing too. Since with this smallish sensor field flattening isn't needed anyway I would expect the separation to be less important. I'm afraid I'm not sufficiently knowledgeable on optics to answer the question. I would like to hear from an optics expert myself. If we had almost limitless clear night skies I'd do a test with various spacings but with clear skies so scarce I'm very reluctant to use them for anything other than imaging.