What kind of camera is the best for high pixel or high zoom celestial photography? Thank you. How about Canon SX40?

The bigger the bottom, the better, because the bigger the Cmos, the better the noise control and the wider the wide angle, which is more suitable for shooting stars in large scenes.

So sx40' s DC of 1:2.3cmos is simply not feasible.

To shoot the starry sky, it is suggested to start with APS-C frame, and generally use Quan Huafu, and the medium frame is better. It is recommended to choose a model with high sensitivity and good noise control for long-term exposure. APS-C has Pentax K5 and Nikon D7000, and Quan Huafu has Canon 5DII and Nikon D800, but the pixels are a little high, and noise control is difficult to control, while starry sky shooting cannot take advantage of high pixels in detail; Forget the medium format, it's too expensive. The cheapest Pentax 645D is enough for you to buy a car.