Starry Night's asteroid data file (the Asteroids.txt file in your Sky Data folder) contains a selection of interesting objects. There are far more such objects available than we include in Starry Night; if we included the hundreds of thousands of known asteroids, the average home computer would not be able to run the simulation. In addition, the orbital data for some near-Earth asteroids (NEOs) are changing so quickly that we do not include them, in the interests of accuracy.
If there is a particular asteroid you would like to see that is not already included in the Asteroids.txt file, please consult the preformatted asteroid file kindly prepared by the International Astronomical Union. The data in this file is already formatted for use in Starry Night. Locate your asteroid in this file and copy the corresponding row of text. Open your Asteroids.txt file and paste the new line in at the top, making sure the columns line up. Save the Asteroids.txt file.
See the attached screenshot to understand the formatting of the text file - i.e how the columns line up. In the screenshot, the last five asteroids have been added manually to the list. Notice how all the decimals line up.
When you next start Starry Night, you will be asked whether you want to update data files. Say no, because if you say yes it will overwrite the changes you made. You will now be able to search for your asteroid by name using the Find tab.