Depending on how you want to use it, observation or shooting (imaging), generally choosing a telescope based on two data: focal lengths and focal-to-diameter ratios (focal length/clear aperture, aperture, f). Don't look at some of the statements tens of thousands of times, it's pure nonsense.

Eye observation magnification = telescope focal length / eyepiece focal length

For example, your telescope is 1000mm, the eyepiece focal length is 10mm, and the magnification is 100 times.

The other is the resolving power. The size of the telescope aperture determines the resolving power. In theory, you can use an ordinary refractor with a very short focal length eyepiece to achieve the theoretical magnification.

However, the aperture limits the ability to collect light. Although you can see the target , but it's blurry, and you can't see it no matter how much you focus.

For example, in theory, you can buy a 70mm diameter refractor with a 700mm focal length and a 3mm eyepiece to achieve 233x magnification, but what you see is dark and blurry view, which is meaningless, so regular telescopes will have a maximum magnification. therefore, pay attention when you buy it, if the matching eyepiece exceeds the limit, you will not be able to see clearly.

Of course, the quality of the optical elements used also affects the resolution. If the telescope is used for shooting, that is another story.

Generally, 80-125 times is enough to observe the moon, and 125-200 times is needed to see the details of the lunar surface; Saturn and Jupiter are not difficult to see, 120-200 times are enough, and it is more than 300 times to see clearly. Mars, Mercury, Venus about 400-500 times, Uranus Neptune, don't think about it, the resolution is enough to be a very dark blue dot, you may not be able to find it at first.

1. Beginners for lunar and planetary observation
Medium focal length, small diameter, focal length 800-1500 (generally longer focal length, long diameter and large diameter, suitable for beginners, but bulky, not easy to carry), the diameter of the refractor does not need to be too large, the choice of the magnification adjustment eyepiece is fine, such as TONTUBE The series of astronomical telescopes, the price is not expensive, spending money to buy a better eyepiece is enough to play for a while.

2. Advanced lunar surface, planetary observation
Large-caliber and long focal lengths are needed, 1500-3500 focal lengths are fine. This type of telescope is large and heavy, and there is no such thing as portability. Coupled with the long focal length, an equatorial mount is often needed to assist in tracking, or you need ten minutes to find the target. , looked at it for a few seconds and then disappeared from the field of vision, and the manual operation was completely inoperable. The price is also relatively expensive, and you should also consider the equatorial mount and consider it according to your own budget.

3. Deep Sky Observation
Objects in the deep sky are very dark, and few can be seen clearly with the naked eye. If you want to observe with a telescope, you should choose a telescope with a short focal length (generally larger, and no need for a large magnification) and a large aperture.

Large-diameter binoculars, deep-space photography refractors, and birdwatching mirrors are all fine. The focal length is 300-800mm, and the eyepiece above 30mm is best for high-definition. In other words, the smaller the f-number of the telescope, the larger the clear aperture, the better.