Most DSLR cameras made since 2009 will record high-definition video. This video is usually recorded in one of two high-definition resolutions.

1080p high-definition video records an image that is 1,920 pixels wide by 1,080 pixels high. This is where the "1080" in 1080p comes from, it tells how many pixels of resolution we have on the short side of the frame.

720p high-definition video records an image that is 1,280 pixels wide by 720 pixels high.

The "p" in 1080p means it is progressive scan. This is a video term that means all the vertical lines in each frame are drawn in sequence as opposed to interlaced video where alternating odd and even lines are drawn every other time, as is done with analog television. Progressive and interlaced video isn't of much concern to us as almost all DSLRs use the progressive method.

Not the Best Choice for High-Resolution Planetary Imaging

Although it can be used in special circumstances, we do not generally want to use high-definition 1080p or 720p video for high-resolution planetary imaging. For that, we want to use a mode that will give us 1:1 pixel resolution.

As we mentioned in the first chapter, the problem with using standard high-definition video for planetary photography is that the native resolution of a sensor like that in the Canon T3i, which is 5,184 x 3,456 pixels, must be down-sampled to 1,920 x 1,080 pixels. In this process, a lot of the original resolution must be thrown away. This is not good for high-resolution planetary imaging.

The way to get around this problem for high-resolution planetary imaging is to use either 5x magnified Live View, or Movie Crop Mode to access something as close as possible to the sensor's 1:1 pixel resolution.

High-Definition Video for Specialized Planetary Imaging

There are some cases where using standard 1080p high-definition video might be useful for specialized instances of planetary imaging, such as with a transit of the International Space Station (ISS) across the face of the Sun or Moon.

In these cases, if you want to shoot the path of the ISS in a multiple-frame composite, the 30 frames per second framing rate of 1080p high-definition video can be useful. We are not shooting the ISS at high resolution - we are basically shooting the full disk of the Sun.

This composite sequence of the International Space Station transiting across the face of the Sun. It was made from 41 individual frames taken from a high-definition video shot with a Canon T2i (550D). The 1920 x 1080p video was shot at 30 frames per second through an 80 mm f/11 refractor with a Baader white-light solar filter. The single frames were extracted from the video and stacked together so the path of the ISS could be seen. The yellow color of the Sun was added in Photoshop in post processing.

With an example like this, we can pull 30 or so individual frames from the video when the ISS is in front of the Sun or Moon. ISS transits usually only last around one second, so at 30 fps, we can get 30 individual frames with the ISS in a slightly different position in each one.

We can also use standard 1080p high-definition video if we want to shoot at less magnification to capture the entire disk of the Sun to show the overall location of sunspots or the entire disk of the Sun or Moon, depending on the focal length.