How to choose a custom star map

1. Where the stars come from

A star map is only as good as its data. Look for a shop that names a published star catalogue, such as the European Space Agency’s Hipparcos catalogue or the Yale Bright Star Catalog. All of these place the bright stars in the same positions; what matters is that the shop uses one and says so.

2. The right moment

The sky turns about 15 degrees every hour, so the time and the time zone matter as much as the date. A good builder asks for the time and works out the daylight-saving rules that applied in that place on that date, which have changed over the years. Before you pay, compare the preview with a free astronomy app set to the same night: the bright stars should match.

3. What is on the map

Some maps draw constellation lines and names, some show the moon or planets, and most leave room for your own words: names, the date and place, and a line that means something. Decide what you want before you compare designs.

4. Format and size

Most shops sell a printed poster, often with a frame, and some sell a digital file, canvas or jewelry. Choose a size that fits a standard frame, so you are not paying for custom framing later.

5. The delivered price

Compare what arrives at your door, not the headline price. Unframed prints often ship free while framed ones add shipping that varies by country and size, and sale prices change week to week.

6. Returns

Because every map is personalised, return policies differ more than you might expect: from no-questions-asked refunds to replacements for damage only. Read it before you order, especially for a gift.