DIY Astronomical reflecting telescope I have a 150mm F750 bull mirror, how to configure it?

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In this book, how to do DIY is very detailed. Several design schemes are given.

The shortest size of the main lens barrel depends on the diameter of your lens barrel, the length of the focusing base, the thickness of the main lens holder and the structure of the auxiliary lens base. If the diameter of the lens barrel is 200mm, the optical path length of the focusing base is 100mm, the thickness of the primary mirror bracket is 50mm, and the distance between the secondary mirror bracket and the optical center of the secondary mirror is 50mm, the minimum length of the lens barrel is 750-(200/2)-100+50+50 = 650mm.

150f750 focal ratio f/5, which is a short focal length lens. If its mirror accuracy is high enough, it can not only look at nebulae at low magnification, scan stars and look for coma, but also look at the moon, sun, planets and binary stars at high magnification. Of course, if its accuracy is not high, it will only be used at low magnification, but it is not useless.

Undoubtedly, the focal length of cattle used in landscape photography is too long, and it is only suitable for taking some small local close-ups, such as taking pictures of birds. However, the solar radiation during the day will make the air near the ground fluctuate violently (turbulence), which seriously limits the shooting distance. Therefore, a lens with a long focal length is of little use in landscape photography.