Individual hand-colored engraved celestial cards from the original set of 32 , each showing one or more constellations, and having perforated holes of various sizes (as issued) through which to view the stars of various magnitudes comprising the constellation figures shown on the cards when held to a light source.
In the early 19th century, a set of cards called Urania's Mirror was produced to view the constellations as seen in the Northern Sky in London. According to the accompanying guide book, they were created by "a young Lady," to make the study of astronomy "familiar and amusing." Each card has a colored image of the constellation as interpreted in classical mythology, and holes of various sizes are punched in the card where the stars that form the outline of the constellation are located.
To use the cards, each would be held up to a light source (such as a lantern) to see the stars that formed the constellation shown on the card represented by points of light. The brighter stars would appear larger (as they do in the sky) through the large holes, all the light being diffused by the tissue paper backing the card.
The star cards could also be used outside to revisualize the constellation figures formed by the stars, by holding the star card up to the sky, as long as the moon was bright, or a lantern was used. You probably couldn't literally see the stars through the card against the night sky though - that would be only from the artificial light source when viewed beforehand, presumably indoors, when one was learning to recognize the star formations that comprised the constellation.
Condition: Cards generally very good, the colors bright, noting the usual light toning, wear and soiling. Precision and evenness of execution of the hand-coloring varies from card to card.
Aspin, Jehoshapat. A Familiar Treatise on Astronomy, Explaining the General Phenomena of The Celestial Bodies; with Numerous Graphic Illustrations. Written Expressly to Accompany Urania's Mirror, or A View of the Heavens; Consisting of Thirty-Two Cards, on which are Represented all the Constellations Visible in Great Britain; on a Plan Perfectly Original, Designed by a Lady. 2nd ed. London: Samuel Leigh, 18 Strand, 1825.