Twice a century, Venus crosses the face of the Sun as a small black dot — and in the 1700s astronomers realised that timing that crossing from distant corners of the Earth could reveal the true size of the solar system. James Ferguson's broadside predicted the 1769 transit years in advance, diagramming exactly where the dark disc would track. It sent ships and observers across the globe, Captain Cook's first voyage among them. This is science foretelling the sky and then setting out to measure it — the humble black dot that gave the heavens their scale.

Maker: James Ferguson
Date: 1763
Medium of the original: Plate
Original held by: Published London · Wikimedia Commons
Credit: Published London · Wikimedia Commons
Rights: Public domain, verified
Catalogue number: PA-00990

As chosen: 18 x 24 in, art print, classic frame
Picture	18 x 24 in
Outside size	19.6 x 25.6 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	467	Excellent	Trimmed 2.7%
12 x 16 in	320	Excellent	Trimmed 8.7%
12 x 18 in	311	Excellent	Trimmed 2.7%
16 x 24 in	233	Excellent	Trimmed 2.7%
18 x 24 in	213	Excellent	Trimmed 8.7%
20 x 30 in	186	Good	Trimmed 2.7%
24 x 36 in	155	Good	Trimmed 2.7%

Sizes withheld
Size	Why
8 x 10 in	Wrong shape: a 14% crop
11 x 14 in	Wrong shape: a 13% crop
16 x 20 in	Wrong shape: a 14% crop
24 x 30 in	Wrong shape: a 14% crop
30 x 40 in	128 dpi; a historical scan is never enlarged
36 x 48 in	106 dpi; a historical scan is never enlarged
40 x 60 in	93 dpi; a historical scan is never enlarged