That sounds like a fun project! First grab a star chart for the date and time you want to represent. Pick a few bright stars from each constellation and note their right‑ascension and declination. On your canvas, set up a simple grid—maybe a few inches for each degree—so you can translate the coordinates into spot positions. Once you’ve plotted the stars, sketch the constellation lines lightly, then go over them with the postcards. If you want extra accuracy, a quick lookup on a planetarium app can give you pixel‑level precision for the scale you’re working with. And don’t forget to add a little note on each card about the star’s name or a fun fact—it turns a neat map into a little lesson!