Can I use a digital camera to take pictures of the solar eclipse?

Photographic Observation of a Total Solar Eclipse

For most astronomy enthusiasts, the total solar eclipse on July 22 is the closest, costs the least, and takes the shortest time. It was the total solar eclipse that was witnessed by the largest number of people and lasted the longest time. If we miss this opportunity, we will have to wait another 25 years to see a total solar eclipse again in our country (on March 20, 2034, a total solar eclipse will be visible in parts of Tibet and Qinghai).

Selection of photographic equipment

1. Camera

In recent years, SLR digital cameras have gradually replaced SLR film cameras. Most of the optical pixels of SLR digital cameras All are above 10 million. SLR film cameras use film, and SLR digital cameras use CF cards (memory). There are two types of film: negative film and positive film. Positive film is also called reversal film and slide film. Negative film has a wide exposure latitude, even if it is slightly overexposed or underexposed. The positive film has a small tolerance, and it is okay to be slightly underexposed, but it is not good to be slightly overexposed, and it may even be scrapped. For photography with a SLR digital camera, its nature is similar to that of a positive film, that is, it cannot be overexposed, but it can be slightly underexposed. Because if the photos taken are somewhat underexposed, they can be corrected in the computer picture software later.

It is important to make good use of the camera's exposure compensation function. The camera's exposure value EV can be adjusted in one-third steps from -2 stops to +2 stops. Usually, when shooting ordinary scenery, the exposure value is 0, which means that the exposure is neither over nor under exposed. When shooting with a digital camera, under normal circumstances, the exposure value should be based on the principle of erring on the side of less than too much.

SLR digital cameras can be divided into two types: full-frame cameras and non-full-frame cameras. For the same lens focal length, the photos taken by a full-frame digital SLR camera are the same as those taken by a SLR film camera, but the focal length of the photos taken by a non-full-frame camera will be greater than the focal length of the lens. For example, for a Canon SLR digital camera, the focal length of the lens must be multiplied by 1.6, that is, a photo taken with a 100 mm focal length lens is equivalent to a photo taken with a 160 mm focal length lens for a SLR film camera; for example, Nikon and Sony's SLR digital cameras must be multiplied by 1.5 , that is, a photo taken with a 100 mm focal length lens is equivalent to a photo taken with a 150 mm focal length lens on a SLR film camera. The focal length of the lens is increased, which is beneficial for taking photos of a total solar eclipse.

The sensitivity ISO of digital cameras has specifications such as 100, 200, 400, 800, 1600 and 3200. When shooting a partial solar eclipse and bright scenery, use a sensitivity of 100. When photographing a total solar eclipse and its ground scenes, you can use a sensitivity of 200 to 800 or even higher. In addition to having a camera, you should also have a stable tripod, gimbal, shutter release cable, Bader film, and adapters for the camera and telescope. When shooting with a telephoto lens, you can choose a high-quality gimbal that can rotate at any angle.

2. Lens

To take photos of the total solar eclipse, you can choose a camera lens. Usually, a total solar eclipse can be photographed with a lens focal length of 300 mm or more. If the focal length is not long enough, you can add a teleconverter. There are usually two types of teleconverters: X1.4 and X2. After the teleconverter of the X2 is connected, the focal length of the lens can be doubled, but the aperture value is also doubled (the actual aperture light transmission becomes smaller). For example, if a lens has a focal length of 400 mm and an aperture of 2.8, and is connected to the X2 teleconverter, the focal length becomes 800 mm, and the aperture becomes 5.6 (the larger the aperture number, the smaller the light transmission). After the teleconverter is connected to the lens, the quality of the photos taken by the camera becomes slightly worse.

3. Telescopes

There are three types of telescopes: refractor telescopes, reflecting telescopes and catadioptric telescopes. To photograph a total solar eclipse, a refracting telescope is usually used. Because the refracting telescope is small in size, light in weight, and easy to carry; secondly, it has a moderate focal length and a large aperture, so it does not require an equatorial mount (automatic tracking). The aperture of a refracting telescope for photographing a total solar eclipse is usually 80 mm, and the focal length is more than 500 mm. For similar telescopes of the same caliber, the longer the focal length, the smaller the aperture. Reflecting and catadioptric telescopes usually have larger apertures, longer focal lengths, and smaller apertures. For the same shooting conditions, the smaller the aperture, the longer the exposure time. Therefore, large-diameter reflecting telescopes and catadioptric telescopes, due to their long focal length and small aperture, need to be equipped with an equatorial mount for automatic tracking in order to be effective. To use a telescope to photograph celestial objects, you must prepare an "adapter" to connect to the camera. Different brands of cameras have different "adapters".

Photography and Observation of Total Solar Eclipse

1. Photography of Belize Pearl

Characteristics of Belize Pearl: First, the duration is short, only one or two seconds Second, the brightness changes greatly during the process, from very bright to very dark (eclipse), or from very dark to very bright (light generation).

Key points for shooting:

1. A few seconds before the eclipse occurs, remove the filter in front of the telescope or telephoto lens.

2. Adjust the camera shooting mode to the continuous shooting position, that is, how many pictures can be taken per second.

3. Adjust the camera shooting method to aperture priority (A), usually using the maximum aperture, or adjust it to automatic (P), but cannot use manual (M), because when When the brightness of the bead changes, the exposure adjustment of the continuous shooting cannot change with the change of the light of the subject. It will either be overexposed or underexposed.

4. Use manual focus to adjust the focus to infinity, and make appropriate fine adjustments back and forth to ensure that the focus is very accurate.

5. Adjust the exposure value EV to -0.3 or 0.

6. Adjust the sensitivity ISO to 400 or 800.

When the food is still one or two seconds away from happening, press the shutter. In this way, through continuous shooting, the entire process of the appearance of the bead can be captured. After taking the photo, check to see if the exposure is accurate. If the exposure is slightly overexposed, adjust the exposure value slightly lower the next time you take a photo of the bead (before light exposure); otherwise, adjust the exposure value slightly higher.

2. Photographing prominences and chromatic spheres

Since prominences and chromatic spheres appear almost at the same time as Belial beads, if you photograph Belial beads, you can usually photograph prominences and chromatic spheres. Color balls, their shooting methods are basically similar. However, the brightness difference between them is large, making it more difficult to photograph prominences and chromatic balls. If you specialize in photographing solar prominences and chromatic spheres, a telescope is better than a telephoto lens on a camera, a telephoto lens is better than a short telephoto lens, a higher ISO is better than a lower sensitivity, a large lens aperture is better than a small lens aperture, and a fast shutter speed is better than a slow shutter speed. , continuous shooting is better than single shooting, and accurate exposure is better than overexposure.

3. Photographing the corona

After taking pictures of the bead (after the eclipse), you can adjust the camera sensitivity ISO to between 400 and 1600 to take pictures of the corona. Since this total eclipse lasts about 5 minutes, we can have time to take more pictures. If you use different exposure values, take more underexposed and overexposed photos of the corona. Adjust the camera to shoot with different color temperatures to capture colorful corona. If you shoot with a high color temperature, you can shoot a blue corona; if you shoot with a low color temperature, you can shoot a red corona. The focal length of different lenses can be changed for shooting. Shooting with a long focal length can capture close-ups of the corona; shooting with a short focal length can capture the corona, Mercury, Venus and ground scenes. If you use an equatorial mount to automatically track and take long-term (several seconds to tens of seconds) wide-angle shots, you can take pictures of the corona, Mercury, Venus and many bright stars. During this total solar eclipse, Mercury is to the east of the sun, with an angular distance of about 10 degrees; Venus is to the west of the sun, with an angular distance of about 44 degrees. It is more difficult to capture Mercury, Venus and a total solar eclipse in the same photo this year than last year.

4. Photographing the "Gourd String" of the total solar eclipse

Equipment requires a tripod, shutter release cable, camera, short-focus wide-angle lens and Bader membrane (filter). It is important to know the altitude and azimuth angle of the sun during the eclipse. For example, when photographing the gourd string of a total solar eclipse in Wuhan, Hubei, we can see from the table that when the eclipse was at its peak, the solar altitude angle in Wuhan was 48 degrees and the azimuth angle was 93 degrees (almost due east). When framing the camera, the position of the sun during the total eclipse should be placed in the center or the best position of the photo, and if possible, the ground scenery should also be included. Last year when we photographed the "Gourd String" total solar eclipse, the altitude angle of the sun's movement changed from large to small (the sun gradually approached the horizon); when we photographed the "Gourd String" total solar eclipse this year, the altitude angle of the sun's movement changed from small to large (the sun gradually approached the sky). top). Once the camera is fixed, do not move it, focus it properly, and take a photo every 5 or 6 minutes on the eve of the first loss. During the eclipse period, different exposures should be used, that is, several photos should be taken with underexposure and overexposure. The accurate exposure of this photo is the most important, which is related to the success or failure of the gourd string photo of the total solar eclipse. Because the blueprint for the gourd string photo of the total solar eclipse was edited using computer software from this photo.

5. Recording and shooting of the camera

The entire process of the total solar eclipse can be captured, focusing on the period from the eclipse to the onset of light. We can approach the camera and tell the time loudly in front of the "Shiji": "What time, minutes and seconds is it now in Beijing time?" After the "light generation", we can tell the time again to the camera. After the total solar eclipse is over, based on the two time reports, photography and recording, we can sort out the local eclipse and light appearance times as well as the duration of the total solar eclipse. Since this total solar eclipse lasts for a long time, 30 seconds after the eclipse occurs, the camera can be turned to take pictures of the surrounding sky and ground scenes, as well as the nervous activities and conversations of people around it. When the "light" was still 60 seconds away, we pointed the lens at the black sun again to shoot.

6. Photographing ground scenes

Since this total solar eclipse lasts for several minutes, there is time to observe the scenery outside the corona. We can shoot the scenery on the horizon from the east, south, west and north, shoot the activities of livestock and flowers and trees, and shoot the silhouettes of fellow enthusiasts. During the total eclipse, it is recommended not to use flash but to use a tripod when photographing scenery.

To sum up, to observe and photograph a total solar eclipse, you must be very familiar with the observation and photographing equipment and practice photographing the sun and moon. A detailed observation plan and program must be made in advance, especially from 10 minutes before "eating" to 10 minutes after "light", when and what to do, a detailed timetable must be made, and a predetermined plan must be used. The plan guides your own observation actions. (Excerpted from "Astronomy Enthusiasts" Issue 5, 2009)

Special reminder:

1. Never look directly at the sun with the naked eye or any optical equipment (such as a telescope)!

2. Do not shoot directly with a camera (a special filter must be added) to prevent damage and burning of the camera.