The more pixels you have, the more resolution you have. The more pixels you have, the bigger the print you can make.

But the ultimate print size that you can achieve with your particular digital file of an astronomical is dependent on a number of different factors, such as viewing distance, optical quality and resolution of the imaging system, accuracy of tracking during long exposures, seeing, accuracy of focus, quality of support frames and calibration, and the signal-to-noise ratio in the final image.

If all of these factors are optimized, and the signal-to-noise ratio is high, you can also use interpolation to increase the file size and make bigger prints.

Early DSLR cameras that have 6 megapixel sensors have a 3000 x 2000 pixel array. The latest have 10, 12 and even 15 megapixels. Professional DSLR cameras currently have up to 24.5 megapixels. These numbers may continue to increase in the future.

Remember, for an inkjet printer, image resolution in ppi (pixels per inch) does not equal print resolution in dpi (dots per inch). Desktop inkjet printers usually print in the 720 - 2880 DPI range. You will usually need anywhere from 150 to 360 pixels per inch for excellent prints on today's photo quality inkjet printers.

Some high-end commercial printers do print in pixels-per-inch. With these printers, there is a 1:1 correspondence between the pixel in the image file and the pixel in the printer. These printers usually need about 300 pixels per inch to make the output print look like a continuous tone image.

The following chart shows the approximate^* sizes needed for good quality prints. With a high signal-to-noise image, you can probably print somewhat larger with little loss of quality.

* Sensor size, number of pixels, file size, and print sizes are approximate, and most are rounded off.