Video	Stack	Final
This is what lucky imaging can accomplish. A video is shot of Mars to record a large number of frames (left). AutoStakkert! is used to pick out the best frames and stack them (center). The stack is then sharpened in RegiStax with wavelet sharpening, and further enhanced and color corrected in Photoshop (right).

Lucky imaging is the technique we will use for most of our high-resolution planetary photography for close-up views of sunspots, lunar craters, and detail on planets such as Mars, Jupiter and Saturn.

Lucky Imaging means shooting a lot of frames in quick succession and getting lucky in recording some brief moments of good seeing in some of them. Shooting a lot of frames in a short period of time before planetary rotation will blur details usually means shooting video, or recording the Live View video signal out of our DSLR cameras.

Video allows us to shoot hundreds, or thousands of frames, during a short time span of a couple of minutes.

We will then use special software like RegiStax, AviStack, or AutoStakkert! to grade and pick out only the sharpest frames and to align the sharpest parts of the image to compensate for movement due to seeing and tracking. This is called multi-point alignment.

Next the software stacks the best parts of the best frames to improve the signal-to-noise ratio. Stacking means averaging the frames together.

Finally we sharpen the stack with special sharpening methods like wavelets or deconvolution to reveal details that are not apparent at first. These sharpening methods are discussed more in the chapter on image processing.

Even with lucky imaging, you have to be patient and wait for those nights of decent seeing when the atmosphere settles down and gives you a chance to record some high-resolution details on the planets with lucky imaging.

Good seeing is one of the most important things in good planetary photography. If the seeing is really bad, even lucky imaging won't reveal really high-resolution detail.

Ways to Shoot Planetary Video with a DSLR

There are three different ways to shoot video with a modern DSLR. We will discuss each in detail in their respective sections.

• Live View

• High-Definition Video

• Movie Crop Mode

Most DSLR cameras made since 2007 offer a "Live View" video display where you can see what the camera sees on the LCD on the back of the camera. We can record this Live View video with special software to a computer, even with cameras that do not record video at all.

Most DSLR cameras made since 2009 will also record high-definition video in the camera to the memory card. Normal 1080p or 720p high-definition is not the best way to record video for high-resolution planetary work, but it can be useful in certain situations.

Some DSLR cameras offer a special "Movie Crop Mode" that captures only a small central area of the sensor at 1:1 pixel resolution.

1:1 Pixel Recording for High-Resolution Planetary Photography

We discussed the importance of 1:1 pixel recording in Chapter 1 Section 2, but we will review it here briefly.

The secret to high-resolution planetary photography with a modern DSLR is to find one of the methods above that will let you record the image at 1:1 pixel resolution or as close to it as possible. Some cameras, no matter what method you use, will not let you record data at exactly 1:1 pixel resolution, but will come close enough so that you can still take some very good planetary images.

We can usually achieve 1:1 pixel resolution, or closest to it, by recording Live View with 5x magnification, and with the special 640 x 480 Movie Crop mode, so those are the ones we want to concentrate on.

The T2i (550D), 60D and 60Da offer 640 x 480 movie crop mode. This mode does give true 1:1 pixel resolution. The great thing about 640 x 480 Movie Crop Mode is that it records at 60 frames per second.

The later model T3i (600D) offers a variation called digital zoom Mode where you can zoom in to 3x while in 1080p high-definition video mode. This, however, is not 1:1 and is actually quite a bit off. If you have one of these cameras, you are better off recording Live View at 5x for high-resolution planetary imaging.

Even if your camera does not have 640 x 480 Movie Crop Mode, you should be able to record Live View with a 5x magnification factor that will give us exactly 1:1 pixel resolution on some cameras, and as close to 1:1 as possible on most other Canon cameras.

If you have an older DSLR that does not have Live View, you will not be able to record video to use lucky imaging for high-resolution planetary work.

Considerations

For high-resolution planetary DSLR lucky imaging, there are advantages and disadvantages to using the two main methods recommended here: magnified Live View or 640 x 480 Move Crop Mode.

Each of the main 4 pieces of software out there that works for capturing Live View video also implements their captures in a slightly different way.

Here are the main considerations:

• Field of View - A slightly larger field is usually obtained in Live View compared to 640 x 480 Movie Crop Mode. Live View with the T2i (550D), T3i (600D), T4i (650D), 7D, 60D and 60Da will give you 1024 x 768 pixels. This is not a huge consideration if you are shooting a small planet. But if the magnification is increased a lot and a large image size on Jupiter or Saturn is produced, or if inclusion of some nearby moons of Jupiter is desired, or if a larger field is required for lunar or solar work, then this should be taken this into consideration.

• Framing Rate - Do some tests to see what kind of framing rate you get with your equipment as it can vary quite a bit depending on the software and hardware you use. The fastest framing rate you will get will be in Movie Crop Mode with the Canon T2i at 60 frames per second. With a slow laptop, you may only get 8 to 10 frames per second. This difference is significant.

• Compression - Shooting Movie Crop Mode and recording video in the camera as a MOV file format uses H.264 compression. This is an excellent method of compression, but it is still what is called lossy. This means that some information is thrown away and lost to achieve the compression. In a perfect world you would want to use lossless compression, or no compression at all, but recording video is a compromise between file size and image quality. Out of the four planetary imaging programs that we will cover: Astro Photography Tool, Backyard EOS , EOS Camera Movie Record, and Images Plus; and recording video directly in the camera; only Images Plus lets you record Live View video uncompressed. The uncompressed video file sizes produced by Images Plus are, however, enormous. Recording 1,000 frames produces a 2 gigabyte file.

  On the other hand, we don't really know exactly what Canon is doing to the data from the sensor before it is sent to the Live View video signal because Canon keeps this information proprietary.

  All in all, compression and data handling are probably not something we need to worry about. I have gotten good results with the H.264 MOV compressed images as well as the files produced by the programs that record Live View.

• Hard Drive Space - In these days of 1 Terabyte and larger hard drives, you wouldn't think you would have to worry about having enough hard drive space. But keep an eye on this when you are recording planetary videos, particularly if you are using Images Plus' uncompressed SID file format.

  Whereas a one-minute compressed MOV file with 3,600 frames shot at 60 fps in the camera with Movie Crop mode is only 166 megabytes, a 3,600 frame uncompressed SID file is 7.2 gigabytes. I only have an 80 gigabyte hard drive in my laptop when I'm working in the field at a remote observing location. I normally have about 40 gigs free, but if you are working over the course of a couple of hours, you can fill up a hard drive quicker than you might think.

  If you are recording videos directly to the memory card in your camera, you also need to be aware of how much space you have on the card, and on the speed rating of the card. Canon recommends at least a 6x speed card for recording videos.

Framing Rates

The whole point in lucky imaging is to record a lot of frames in a short period of time before planetary rotation can blur the final stacked image. Software then goes through all of the frames and picks out only the best ones to be stacked.

The number of frames that you can record in a particular time period is called the framing rate. If you can record 30 frames in one second, you have a 30 frames per second framing rate. Frames per second is abbreviated "fps", so you would have 30 fps.

The framing rate with 640 x 480 Movie Crop Mode recorded in the camera is 60 fps.

The framing rate with Live View being captured by software is dependent on the speed of your computer, its hard drive and its operating system.

With a Windows 7 computer with a fast hard drive, you can usually record about 14-28 frames per second with Images Plus Camera Control v4.5. and 25 - 30 fps with EOS Camera Movie Recorder .

With a slower computer, you may only get 5 to 8 fps.

The number of frames per second that you can record is important because you have a limited amount of time you can record before planetary rotation blurs details in the final stacked image.

The more frames per second that you can record, the more chance you have of getting some with good seeing and producing a better image.