There are several ways to achieve a near to the perfect collimation of the Newtonian telescope. The final phase, which is the proof of perfection is the star test. I had a serious problem with that test, my stars appeared triangular!This photo-set could be a good example of the typical "pinched optics" problem. Even the atmospheric instability can not hide it. The top row of the composite image depicts my typical hyperfocal stars, the bottom row - prefocal. Star in focus - the dot in the center (still looks triangular).
