Tips for Photographing Partial and Annular Solar Eclipses
Photographing a partial or annular solar eclipse requires some thought. In most circumstances you cannot just point your camera at the Sun and take a picture. The Sun is simply too bright for your camera (and your eyes). The exceptions are when weather presents a thin layer of clouds that act as a solar filter or the Sun is close to the horizon (such as sunset or sunrise). Even then, you must be extra cautious so as not to damage your camera or eyes.
The simplest method is to take pictures of pinhole projections/shadows. Find a tree with leaves or something that has many little holes. Look at the shadow and if you can see bright sunlight then you should be seeing projections of the partial or annular solar eclipse. To take a picture like this just use the automatic or normal daylight settings and a regular lens.
A better, crisper image can be accomplished by taking a picture of a projected view. If you have a telescope or binoculars on a tripod you can set up a projection system.
Taking a picture of the projected image (with some background) is easy. Just set the camera to automatic for daylight or use the light meter for the exposure. Focus on the projected image and take the picture.
Solar filters should be designed specifically for your optics. Making your own solar filter requires a significant note of caution and the use of the proper materials. You should also pay particular attention to how the filter is mounted to the camera optics. A sudden wind gust could be tragic. Click the link for more information about building your own Solar filter mount.
Dedicated solar filters produce images in a variety of colors. The most common are blue and orange. Treat these filters delicately and make sure they remain free of scratches or blemishes. If a layer of the filter is deteriorating, the filter is useless. Solar filters are available for most brand name cameras and lenses. They are only recommended for longer focal length (higher magnification) setups as shorter focal lengths produce only a dot on the image.
Advanced solar filters such as hydrogen-alpha or calcium-k, which are used by astronomers to study various layers of the solar disk, can also be used however they require a bit more expertise. That expertise is best obtained through practice. Because these filters only allow a single wavelength through the image is dimmer and longer exposures are required. As an example, using a Coronado 40mm f/10 hydrogen-alpha telescope with a 2x Barlow lens requires about 1/30 of a second for an exposure of the solar disk and half a second for prominences. To obtain the best images a tracking mount is used. Blur is evident at about one quarter of a second.
Exposure settings and estimates are based on the density of the filter. The exposure calculator supplied online is for a ND5 (Neutral Density) filter. This dark filter only allows a small portion of the light to get through. If you use an ND6 or ND4 filter the settings will be different.
To figure out what works best, practice by photographing sunspots in the days before the eclipse event. If there are no sunspots visible then just try to get the crispest image of the edge of the Sun you can. You might see some faculae or other solar features such as the granulated surface when the exposure setting is best (depends on the type of filter and lens system).
Atmospheric extinction near the horizon will sometimes produce a solar image that does not require a filter. Sunset (or sunrise) images taken without filters can show details of the solar disk. Longer lens lengths are needed (300mm or more) to really get a great image. The problem is the exposure setting. If you have an automatic exposure meter then use a slightly quicker exposure. The meter will be averaging the entire scene and that will overexpose the solar disk.
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