Doppelmayr was a Nuremberg professor who spent thirty years turning astronomy into engraving. This northern hemisphere fixes every star to its position for the year 1730 and then, in the corners, shows the observatories where the measuring was done — the instrument and the result on one sheet. It is a map of the sky that admits how the sky came to be known.

Maker: Johann Gabriel Doppelmayr
Date: 1730
Medium of the original: Plate
Original held by: Ruderman / Wikimedia Commons
Credit: Ruderman / Wikimedia Commons
Rights: Public domain, verified
Catalogue number: PA-00339

As chosen: 20 x 16 in, art print, classic frame
Picture	20 x 16 in
Outside size	21.6 x 17.6 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
10 x 8 in	910	Excellent	Trimmed 5.9%
14 x 11 in	650	Excellent	Trimmed 7.6%
20 x 16 in	455	Excellent	Trimmed 5.9%
30 x 24 in	303	Excellent	Trimmed 5.9%

Sizes withheld
Size	Why
12 x 8 in	Wrong shape: a 22% crop
16 x 12 in	Wrong shape: a 12% crop
18 x 12 in	Wrong shape: a 22% crop
24 x 16 in	Wrong shape: a 22% crop
24 x 18 in	Wrong shape: a 12% crop
30 x 20 in	Wrong shape: a 22% crop
36 x 24 in	Wrong shape: a 22% crop
40 x 30 in	Wrong shape: a 12% crop
48 x 36 in	Wrong shape: a 12% crop
60 x 40 in	Wrong shape: a 22% crop