Andrew Cooper
Aug 13, 2023    Waikoloa, HI (map)
28cm f/10 SCT, NexStar 11" GyPSy @ 104x
Seeing: 5 Transparency: 7 Moon: 0%

A delicate and wide pair consisting of a 7th magnitude orange with a 9th magnitude companion visible 30" northwest

Gaia EDR3 data shows roughly comparable parallax (2.0924 vs 2.2626mas) but notably mismatched proper motions, the primary moving at -25.53mas/yr in RA and -109.27mas/yr in dec, while the companion BD+00 158 is moving at 2.165mas/yr in RA and -9.448mas/yr in dec, probably not a physical system

Captain William Henry Smyth
Dec 24, 1832    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A neat double star [HD 5780 and SAO 109576], bearing both illumination and high magnifying powers. A 8, pale orange; and B 9, clear blue. This, though assigned to Pisces in the Palermo Catalogue, belongs to the Whale, being in the space between the tail of Cetus and the ribbon of Pisces, at about one- third the distance of β Ceti from β Andromedæ, and nearly in the line; being one of the amorphotcæ of which an asterism to be called Testudo was proposed. Piazzi records this object double: " Duplex. Comes 9æ magnitudinis praecedit 1" temporis parumper ad boream;" but the first micrometrical measures I met with, are those of Sir James South:

    Pos. 296° 27'  Dist. 18".87  Ep. 1825.17
             [339°            29".9       2018 WDS]

From which, when compared with my own, I inferred a sensible direct orbital motion 0°.4 per annum; and this has been since confirmed by the Dorpat Catalogue. There is, however, on rigorous comparison, a slight proper motion in space assigned to A—of which probably B partakes—to the following amount:

    B.... RA +0".03 Dec. -0".28
    T....    +0".01      -0".32
   [Gaia DR2 -0".025459  -0".109155]

[Gaia DR2 data shows differing parallax (2.0455 to 1.7823mas) with the companion 230ly further away. The current separation is 30" @ 339°, about right for the high proper motion primary passing the background star moving south and slightly west from the historical observations above]

― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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