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09.30[CET] Clear and bright but the eastern sky is plastered in persistent vapour trails! The seeing is ridiculously soft, shaking violently and the wind blowing into the dome.
13.30 Lunch is over but not a single worthwhile image so far.
The 2x Focal Reducer arrived but it proved unable to focus the telescope + 60MT etalon system once fitted. The T-S focal reducer has a focal length of about 10cm or 4". I have fitted the reducer as close as physically possible to the front of the Lunt etalon's collimation lens.
It won't work. The correction is far too strong.
I have now been advised to forget the focal reducer and just move the MT etalon in and out until I find the best tuning point. In conjunction with the pressure tuning knob on the etalon and the secondary focuser for the camera.
Unfortunately the sky is heavily clouded this afternoon. With rain promised for later. So I can't experiment with etalon distance and tuning until it clears. It is blowing a gale into the dome as well!
A bit of sun and it proved to be beneficial to use the previous distance. 264mm inside focus
480-264mm = 216mm to the MT etalon housing's shoulder. When the actually sun shines I am using most even brightness as my reference for best tuning.
I have now been advised that it is the 60MT etalon module which needs to be moved nearer the objective.
None of this makes any sense. The etalon is neutral in power. So it does not affect the focal length of the 15cm/ 6" f/10 objective. Adding the focal reducer to the bare etalon instantly produces a 4" /10cm focal length. Because that is the native focal length of the reducer. If the beam was converging at f/10. Then the combined focal length becomes something even shorter than 10cm or 4"! The only place that the focal reducer will work is if it is just inside focus. Which is not the point at all. The idea is to feed the etalon with an f/7 converging light cone.
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