Discussion on the selection of astronomical telescope

To watch the nebula, it is best to use a telescope with a small focal ratio. Reflective telescopes are suitable for viewing nebulae because the focal length of reflective telescopes is shorter than that of refractive telescopes. The focal length is brighter than a short telescope! Of course, it also has something to do with caliber. The larger the aperture, the brighter the nebula. If you don't want to buy a cheap large-aperture reflective telescope, choose a refractive telescope with a small focal ratio. APO telescope is a bit expensive. Ordinary refracting telescope has chromatic aberration, but you don't have photography. Just look around. Because it is difficult for the human eye to see the color of the nebula. Only CCD can continuously collect colors, and most of the nebula pictures we see on the Internet are colors obtained by long-term exposure with astronomical telescopes. So if you want to shoot nebulae, you must choose the APO telescope, at least the ED telescope. The cheapest one can only choose a reflective telescope. But if you just look at the nebula, then choose a large ordinary short-focus refractive telescope with a diameter of at least 152mm, and then look down at the nebula! The price is around 5000 to 8000.

You may want to buy a refractive telescope with a short focal length, but it is more expensive. Now there are refractive telescopes with a diameter of 220mm, but the price is tens of thousands!

What about the catadioptric telescope? To tell the truth, reflecting telescope is not suitable for seeing nebulae, because the focal length of reflecting telescope is mostly above f/ 10. This kind of telescope is suitable for observing planets such as Jupiter and Mars. Moreover, large-caliber telescopes are quite expensive, and most brands have to pay tens of thousands of yuan for folding reflecting telescope above 203mm!

To sum up, if you don't want to buy a reflective telescope with cheap reflection, then choose a telescope with ordinary refraction and short focal length ratio, and choose an apo telescope with a caliber of 127mm or an ED telescope with a caliber of 127mm or above, which most people can't afford. Ordinary aperture 152mm, focal ratio between f/6 and f/8. Although the aperture 152 is a bit heavy, the aperture is large, the brightness is high, and more nebulae are seen. You may want a focusing binoculars with a focal length less than f/6. No way, this is one reason why modern super-large-aperture telescopes, such as the 2. 1 m telescope developed by China Zhongke Company and the American super-large-aperture 8-meter astronomical telescope, all use reflection. Reflective telescopes are suitable for observing nebulae because the focal length ratio can be made very short.