Taking things for granted (again!)

Now the moon is preventing any serious deep sky imaging and aircraft contrails are hazing out the transparency I am using the present run of cloudless evenings to try and pin down some lingering problems. Some distortion at the edges of the field of my Newtonian have been of some concern with my main suspects being collimation, pinched optics or the CLS filter. Various tests eventually eliminated each of these which left me wondering if the distance between the camera sensor and the Baader coma corrector was optimum. I had always assumed I was using the correct spacers (supplied by Baader) with my T adapter so never suspected there was a problem. Shortening the distance by about 4 mm for a quick test was easy to achieve and immediately revealed that the distance was indeed a critical factor and was worth investigation. Trial and error established that the distance needed extending if anything but achieving this without getting a custom adapter made would be difficult. However, after rummaging through my bits & pieces and re-assembling my T adapter in a way it wasn't designed for I did manage to achieve an extension of about 3 mm with the camera clinging on to a minimum of thread. The improvement was very pleasing and quite surprising in its magnitude so once again the lesson of never taking things for granted has been learned.

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