Welcome to my new series with technical curiosities in the field of astronomical equipment and optics. I will start with the telescope, the most popular among astro amateurs. This type of telescope allows lovers of the night sky to get an instrument with a large lens diameter at the best price. I invite you to read.
Although its first version built by Newton in 1668 was a small one with a mirror with a diameter of 25 mm, it is today that the mirror telescopes give us the largest available diameter at the best price. And the bigger it is, the brighter and sharper the picture will give us an instriment. See how simple it is. The Newton's telescope consists of an optical tube, completely open on one side, the main mirror, the secondary mirror and the focuser, equipped with focus adjustment. The secondary mirror is fixed on the so-called spider, or a few metal rods that obscure the main mirror. The light falls into the tubes and is focused by the main mirror. Then the image is reflected from the secondary mirror at a 90-degree angle to the spectacle lift, where it goes to a specific eyepiece. When we sharpen the image, we do not see the secondary mirror with the spider, which after all cover a large percentage of the surface of the main mirror.