Significant moments deserve memorable commemorations, but most gifts are mass-produced. The night sky's configuration is unique to every time and place.
Build a web app that generates high-quality prints of celestial arrangements for user-specified dates and locations. Include personalization options.
Target the wedding/anniversary market through Etsy and Instagram ads. Charge premium prices for physical prints.
Start with a simple generator using existing astronomical APIs, then add printing fulfillment.
The risk is competition from existing star chart services.