Urania's Mirror (1825) is one of the most charming objects in the history of popular astronomy: a boxed set of 32 hand-colored constellation cards, each engraved by Sidney Hall and pierced with pinholes at every star's true position — hold a card up to a candle or window and the constellation appears exactly as it stands in the night sky. This card gives Andromeda, the chained princess of Greek myth, her full theatrical due: gold shackles at wrist and ankle, a rose-pink gown, and her body used quite literally as a star chart, with labeled points for Alpheratz, Mirach, and Almach marking real catalogued stars along her arms, waist, and trailing foot. Two neighbor constellations share the card's edges, per period convention — the obsolete Gloria Frederici (a sword bound in laurel, upper left) and Triangula (lower right). What to notice: this is functional astronomy dressed as parlor entertainment, published for a Regency-era public newly hungry for science it could hold in its hands.

Maker: Sidney Hall
Date: 1825
Medium of the original: Plate
Original held by: Wikimedia Commons
Credit: Wikimedia Commons
Rights: Public domain, verified
Catalogue number: PA-00261

As chosen: 12 x 18 in, art print, classic frame
Picture	12 x 18 in
Outside size	13.6 x 19.6 in
Depth	0.9 in (22 mm)
Weight	[[REAL PROOF NEEDED: shipped weight per size and frame]]
Hanging	[[REAL PROOF NEEDED: hanging hardware Prodigi fits to this frame]]
Material	Enhanced matte art paper, 200 gsm; acrylic glazing
Made in	Charlotte, North Carolina, by Prodigi

Before a size goes on sale, the file is measured against it: pixels per inch at that size, how much of the picture a crop would lose, tone and sharpness. A size that fails is not offered, so there is nothing to choose wrong.

How the print check works

Sizes offered
Size	dpi	Grade	How it fits
8 x 12 in	298	Excellent	Trimmed 4.9%
12 x 16 in	209	Excellent	Trimmed 6.5%
12 x 18 in	199	Good	Trimmed 4.9%

Sizes withheld
Size	Why
8 x 10 in	Wrong shape: a 12% crop
11 x 14 in	Wrong shape: a 11% crop
16 x 20 in	Wrong shape: a 12% crop
16 x 24 in	149 dpi; a historical scan is never enlarged
18 x 24 in	139 dpi; a historical scan is never enlarged
20 x 30 in	119 dpi; a historical scan is never enlarged
24 x 30 in	Wrong shape: a 12% crop
24 x 36 in	99 dpi; a historical scan is never enlarged
30 x 40 in	83 dpi; a historical scan is never enlarged
36 x 48 in	69 dpi; a historical scan is never enlarged
40 x 60 in	59 dpi; a historical scan is never enlarged