How was the nebula picture taken?

If you want to take pictures of nebulae, you need an equatorial plane. The principle of equatorial telescope is very simple. Since the earth rotates from west to east, you can design a device that rotates from east to west so that you can rotate with the stars in the sky, so that your camera can expose the target you want to shoot for a long time.

The equatorial camera for photography naturally requires accurate tracking and smooth operation, and it also needs a certain bearing capacity to support the camera, lens or telescope.

Working principle of equatorial telescope

This is the most important step to adjust the equatorial plane-the polar axis. Because China is located in the northern hemisphere, it has a great advantage, that is, it has a Polaris very close to the north pole of the celestial sphere. Adjusting the polar axis of the telescope according to the Polaris means that the right ascension axis of the equatorial plane must be completely parallel to the rotation axis of the earth. In this way, the telescope can track the stars in the sky perfectly. The equatorial plane is just an instrument, just like a camera. People who don't hold cameras are called photographers.

Fishbone focusing plate

So, how to focus when shooting nebulae? Camera focusing can be assisted by something called "fishbone focusing board", and its principle is also very simple. It is to observe whether the star awn generated by the star point is symmetrical through the focusing board, and the focusing will be accurate when it is completely symmetrical. Of course, you can also directly find a star with higher brightness and slowly aim it at the screen in the current digital SLR. Nebulae, like stars, are almost infinite, that is, on a focal plane, so they can be focused by stars.

Nebula contrast photograph

As mentioned earlier, shooting nebulae usually takes a long time to expose. Then the problem comes again. How long does the exposure take? It is difficult to generalize this, but as far as digital SLR cameras and CCD astronomical cameras are widely used at present, it is acceptable to shoot the brighter part of the bright nebula core at an exposure below 180 seconds, taking the telescope with the focal length of F4-F6 as an example. For visible nebulae, such as Orion Nebula, even exposure of more than ten seconds can capture its core. It is necessary to expose a large number of dim nebulae and dim parts around bright nebulae 10- 15 minutes.

Orion molecular cloud complex under 35mm lens.

The central part of Orion molecular cloud complex photographed with 200mm lens.

Orion nebula

The 100% screenshot of the smaller nebula NGC 1999 in the upper right corner was taken by a 480mm focal length telescope, which is located at the lower right of the Orion Nebula.

The next step is framing, which is the choice of lens or telescope focal length. In fact, any focal length can be used to shoot nebulae, but it should be aimed at targets in different horizons. The visible area of some nebulae is so large that even the field of view of a 50mm standard lens can't fit; Some are very small, 1000mm telephoto lens or telescope is only the size of a soybean.

Xingyun factory

Moon photograph

Jupiter photo

Nebula shooting equipment