Photographic equipment for direct focus photography

Usually, the focal length of the telescope is not short, the focal ratio is not bright, and the celestial body is dim, which takes a long time to expose. But the earth will rotate and the sky will move. If exposed for a long time, won't the target celestial body run away? In order to overcome this problem, direct focus photography needs a lot of auxiliary equipment. Let's see:

Camera part: monocular camera (preferably mechanical camera with B shutter and no electricity), cable release.

Telescope part: any kind of telescope (preferably high quality, large aperture and small focal ratio)

Equatorial Observatory (firm and stable is preferred). Star guiding telescope, eyepiece star guiding monitor, catalog map, recording equipment, pocket stove red flashlight.

Direct focus photography pays great attention to instruments, especially telescopes and equatorial planes. This is because the object in direct focus photography is small and dark, so exposure often takes dozens of minutes, or even an hour or two. In such a long exposure time, the quality of the equatorial plane has a great influence on the quality of photos, and it also has a direct impact on the photographer's physical strength (because it is not as tiring as guiding stars). Although equatorial telescope is very important, it is the quality of telescope that directly affects the imaging quality. Advanced telescopes will definitely take better pictures of stars than ordinary telescopes, so the money of telescopes can't be saved.

Generally speaking, the effect of refractive lens is better than that of reflective lens, especially for astigmatism nebula. But the price of refractor is much higher than that of reflector, so what kind of telescope to use is really a matter of opinion. The author suggests that the principles of choosing a telescope are as follows: refractive type-the aperture is above 10 cm and the focal ratio is not more than 8; Reflective-the caliber is more than 20 cm, the focal ratio is not more than 6, and the brand should be selected from reputable old manufacturers. If large investment is not allowed, refraction 10 cm and reflection 15 cm are the lower limits. If it is smaller, the decomposition energy and light collection ability will not be enough.

In addition to telescopes and equatorial telescopes, direct-focus photography also costs money, which is the peripheral equipment for guiding stars. The star guiding equipment includes a star guiding platform, a star guiding telescope, a star guiding monitor and two eyepieces (one at high magnification and one at low magnification). The price of these things can be high or low, but it is definitely not a small expense.