Andrew Cooper
Feb 19, 2022    Waikoloa, HI (map)
20cm f/6 Newtonian, Cave Astrola @ 136x
Seeing: 8 Transparency: 6 Moon: 85%

Tegmine is an easy split with decent conditions, a gulf of dark beween the 5" ζ1 Cnc and ζ2 Cnc pair, ζ1 Cnc itself is just barely split in moments of good seeing, the ζ1Cnc B companion visible 1.6" to the northeast, ζ1 Cnc and ζ2 Cnc are both pale yellow

This trio (and unseen companions of ζ2 Cnc) is a gravitationally bound system, Gaia EDR3 data shows matching parallax and high proper motion...

             parallax  PM RA       δ
    ζ1 Cnc A   40.88     118.3  -148.4 mas/y
    ζ1 Cnc B   40.95      58.8  -120.9
    ζ2 Cnc     41.15      36.9  -150.

9

Andrew Cooper
Mar 24, 2020    Waikoloa, HI (map)
20cm f/6 Newtonian, Cave Astrola @ 61x
Seeing: 6 Transparency: 7 Moon: 0%

A pretty double as the AB 1" pair is not spilt tonight, yellow and yellow with 5" separation

Captain William Henry Smyth
Mar 25, 1832    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A fine triple star, just below the after claws of the Crab, where a shot from Castor through Pollux, carried twice that distance to the south-south-east, will strike it; or it may be found by a ray from Sirius through Procyon, extended to half their distance beyond. But there is much shade on the authority which designates it Tegmine. A 6, yellow; B 7, orange tinge; C 7½, yellowish, No. 6 of Piazzi's Hora VIII. This very interesting physical object forms 24 ♅. I., and 19 ♅. III., and by modifying the dates and diameter of A for distance, we obtain a point of departure from whence an extraordinary retrograde motion is exhibited. The best interval measures for comparing with my own are as follow,—those of Piazzi being deduced from his RAs and Decs., which of course cannot demand implicit reliance:

    ♅.   {Pos. AB   3° 28'  Dist. 1".00}  Ep. 1781.90
         {     AC 181° 44'        8".05}
    P.         AC 159° 00'        6".47       1800.00
    H. and S.  AC 158° 17'        6".24       1822.14
    S.         AB  57° 50'        1".09       1825.27
    H.   {     AB  35° 35'        1".01}      1830.44
         {     AC 155° 52'        5".35}
    D.   {     AB  30° 48'        1".09}      1831.30
         {     AC 150° 17'        5".59}
    Σ.   {     AB  21° 30'        1".13}      1833.27
         {     AC 148° 18'        5".48}
   [WDS        AB 359°            1".10       2021   ]
   [           AC  62°            5".30       2020   ]

This curious and very interesting object has occasioned no little discussion, since ♅ had pronounced it to be a "most minute treble star," and more than forty years afterwards H. and S. had declared A and B to be one "beautifully defined and round." But Sir James South on a second trial saw A " unquestionably elongated," whence a supposition arose that the star B had come from behind A. The distance, however, appears to he very stationary, so that these remarks are extraordinary, and must he imputed to some anomaly. The Rev. W. R. Dawes, of Ormskirk, took it in hand with a 5-foot telescope only. Up to 1830, a direct motion of +1°.25 per annum was assigned to the star B; whereas from the accurate measures of Sir John Herschel and Mr. Dawes, it was afterwards considered to have a retrograde one to the surprising mean amount of -6° 51'. As both these astronomers corresponded with me on the subject, I determined to devote my best powers to it, and though the near object is difficult from convergence, I was able to assign considerable weights to the results: and from them I drew a scheme of the interpolated positions, angular velocities, and projected distances. Hence it follows, that the two close stars perform a binary revolution in about sixty years, while the outer one accomplishes a grand orbital ellipse in 500 or 600 years. It would seem that ♅.'s angle of A and B in 1781, must have been quadranted wrong, for the retrocession from 183°.3, is more explicable than the nf position above given. The mean of my own observations, embracing a period of nearly eleven years, gives a retrograde march of only 2°.77 per annum: or from ♅.'s epoch=3°.78. Sir John Herschel thought, that an entire revolution would have occurred from the epoch of his father's observation to the end of March, 1837, in a periodic time of 55.34 years; which, though not precisely confirmed by me, will be seen to meet the remarkable phenomenon as nearly as the present sidereal knowledge has advanced. "If this be really a TERNARY system," said Sir John, "connected by the mutual attraction of its parts, its perturbations will present one of the most intricate problems in physical astronomy."

Mr. Dawes informs me, that A and B were quite vertical in 1841.32, for the angle of position was then exactly on the zero point; thereby affording a gratifying confirmation of his previous deductions. And it must be noted, that a movement in space has been detected in ζ, in which the comites doubtlessly partake, of the following value:

    P....  RA +0".04  Dec. -0".10
    B....     +0".14       -0".ll
   [Hipparcos +0".02761    -0".15173]

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

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