Resolution is defined by the number of pixels in the digital image. To make the image bigger, we need more pixels.

Images shot with Movie Crop Mode are just 640 x 480 pixels. Images shot with Live View capture are about 768 x 792 to 1024 x 680 pixels.

Figure 1 - Crescent Venus was shot with a 130 mm refractor with a 2x Barlow shot with a Canon T2i (550D) at 640 x 480 Movie Crop Mode. This image was cropped to about 253 x 175 pixels.

This is plenty enough resolution to capture all of the fine details present in the frame on the Sun, Moon and planets, and these images will look great on a computer. But they are not really enough resolution to make large prints.

We can use software to resample the image and give us more resolution. With resampling, the software examines the pixels in the image and creates new ones. It may look at two pixels side by side and average the two together to make a new one in between the originals. Some algorithms that do this are fairly sophisticated and do a pretty good job.

There is a limit however to how much we can resample before the image starts to fall apart. How far we can go will depend on the detail and noise present in the image, and how sharp it is to start with.

For most images with good detail and a good signal-to-noise ratio, we can go about 200 percent. If you try that much and the image looks terrible, try a lower percentage.

• To resample in Photoshop, under the pull-down menus at the top, go to Image > Image Size. The Image Size dialog box will then open (Figure 2).

Photoshop's Image Size Dialog

• Select Percent from the pull-down (Figure 2, Number 1).

• Enter the amount for the percentage you want to resample the image (Figure 2, Number 2).

• At the bottom of the Image Size dialog box, make sure that Constrain Proportions (Figure 2, Number 3) and Resample Image (Figure 2, Number 4) are checked! Bicubic should come up as the default and it is a good choice for resampling (Figure 2, Number 5).

• Click the OK button.

The original 640 x 480 image was cropped to 253 x 175 pixels. After resampling, the image should now be 506 x 350 pixels. This is twice the size of the original, or a 200 percent enlargement. At this point, you should save the file with a new name so as to not overwrite the original.

The resampled image at 200 percent of its original size.