For an observing list I used Argyle's An Anthology of Visual Double Stars. I entered all the pairs discussed in that book into a SkyTools observing list a few weeks ago. It is a richer experience to both observe and learn more about what I'm looking at. Unfortunately, the log function was not working on SkyTools, so I entered my observations into a notebook. It was cold, but fortunately not dewy. I resolved Sirius B in the 80mm while doing the 2-star alignment with the Nexus DSC.
Since I mention it in this entry's title, I'll cover Procyon B first, though I observed it at around 11pm, half an hour before I stopped. Many people will assume more aperture is needed for challenging pairs, but I find this is not always correct. Larger aperture has the resolving power, but it throws out so much more diffraction on bright stars than smaller apertures the view is spoiled. With B at a 5" separation, and at 10.8 magnitude, still within the 80mm's light grasp, this scope still has a chance to resolve it. I first observed Rigel A-BC, which has a 9" separation, to get a sense of the distance 5" would be (slightly less than half). I then observed Procyon, which presented a slightly wavering airy disk and several round concentric diffraction rings. The transparency caused a haze to appear within and around the rings. I saw three fainter, wider stars near to the primary. Using the 10mm I had a sense of a star trying to resolve within that haze but was not certain. I then used a 9mm orthoscopic eyepiece which has a crosshair installed. I was able to hide the primary behind one line of the crosshair (and I impressed myself being able to do so, and the steady tracking of the mount!). It neatly covered the primary and only the diffraction ring and haze appeared. In better moments a small mass appeared to the north (the correct PA) and at roughly the correct separation. It was trying very hard to resolve to a star, and I think it would have if the transparency was better. It moved with the scope and was steady in the same location no matter where I moved it in the field, so I am fairly certain it is not a reflection or an aberration. Still and all, I really wish for the "no doubt about it" clean clear view, and plan to take a similar small aperture up to one of our local mountaintops when seeing and transparency are better to make this observation again.
STF 774 AB: AC seen with 80mm at 48x, faint but solid. AB is elongated at 80mm at 120x. In the 6-inch at 180x, AB is split in poor seeing. AB with a SOC grade 4 orbit, 5587-year period, and will not move much for the next couple of hundred years. Gaia parallax data is missing.
AC: 05h 40m 45.52s -01° 56' 33.3" P.A. 10.00 sep 57.6 mag 1.88,9.55 Sp +A? dist. 225.73 pc (736.33 l.y.)
AB: 05h 40m 45.52s -01° 56' 33.3" P.A. 167.00 sep 2.5 mag 1.88,3.70 Sp +B0III dist. 225.73 pc (736.33 l.y.)
STF 900 AB: 80; 48x: Lovely wide white and 2 Dm B, which is bluish. No parallax range overlap, -26% it is not binary. A Herschel discovery.
06h 23m 46.10s +04° 35' 34.2" P.A. 29.00 sep 12.1 mag 4.42,6.64 Sp A5IV+F5V dist. 37.5 pc (122.32 l.y.)
STF 919 BC: 80; 140x: Beta Mon. BC is elongated in the 80mm at 48x, split nicely with 140x, yellow-white stars, C fainter by a half magnitude. It provides a nice surprise for the observer, to bump up magnification a bit and "discover" a double. Argyle relates how Castelli discovered it by borrowing a telescope from Galileo in 1617. And with the wider A star, which is half a magnitude brighter than B, it forms a small arc. Herschel called it "one of the most beautiful sights in the heavens; but requires a fine evening." There is only Gaia parallax data for A and C, but the two of those together have 77% parallax range overlap, 2,092 AU weighted separation, making a strong case they are gravitationally bound.
06h 28m 49.07s -07° 01' 59.0" P.A. 132.00 sep 7.3 mag 4.62,5.00 Sp B4V+B2V dist. 207.47 pc (676.77 l.y.)
STF 950 AB: 80; 48x: Bright star and its 3 Dm faint wide companion sitting in the middle of a large, sparse open cluster (NGC 2264, Christmas Tree cluster). 18 different components measured over the years. Argyle says the primary is "thought to be the source of a bubble of hot gas which influences the kinematic properties of the surrounding gas and stars." No nebulosity seen! -15% PRO, it is not likely binary.
06h 40m 58.66s +09° 53' 44.7" P.A. 214.00 sep 3.0 mag 4.66,7.79 Sp O7V+B1.5V dist. 281.69 pc (918.87 l.y.)
STF 948 AB: 80; 140x: At first I saw a wide 2 Dm pair at 48x, and the primary did not appear round, so I increased power to 140x and had a hairline split, slight delta magnitude. It is a wonderful 2+1 system. AB has -3% parallax range, so it's a toss-up if it's binary. SOC grade 4 orbit, 733-year period. It was a Herschel discovery.
06h 46m 14.15s +59° 26' 30.1" P.A. 64.00 sep 1.9 mag 5.44,6.00 Sp A3V+A1IV dist. 65.83 pc (214.74 l.y.)
STF 982 AB: 80; 140x: Best view between either scope was 80mm at 140x. Well split 2 Dm, yellow-white and yellow-orange. No Gaia parallax for the primary, though there is a SOC grade 4 orbit 1749-year period.
06h 54m 38.63s +13° 10' 40.1" P.A. 142.00 sep 7.4 mag 4.75,7.80 Sp F0Vp dist. 25.63 pc (83.61 l.y.)
HJ 3945 AB: 80; 48x: Orange and blue, wide pair, very Albireo-esque (it's nicknamed the "Winter Albireo"). -83% PRO, it is not binary.
07h 16m 36.84s -23° 18' 56.1" P.A. 50.00 sep 26.5 mag 5.00,5.84 Sp K3Ib+dF0 dist. 434.78 pc (1418.25 l.y.)
STF 1066 AB: 80; 140x: Wasat. Excellent pair, pale yellow-orange A and very faint B outside A's diffraction ring, a very fine point. Discovered by Herschel the same night he discovered Uranus! 45% PRO, 108 AU WS, 1.9+0.7 Msol, but with a -0.25 proper motion vector -- I wonder because its orbit is taking it in the opposite direction? The orbit does predict a rapid swing from west to east, which is consistent with that -- so proper motion is sometimes not a good indicator of binarity. SOC grade 5 orbit 1418-year period. Another Herschel discovery.
07h 20m 07.39s +21° 58' 56.4" P.A. 229.00 sep 5.5 mag 3.55,8.18 Sp F2V+K6V dist. 18.54 pc (60.48 l.y.)
STF 1110 AB: 80; 48x: Castor. Bright unequal white pair, with 2 fainter wide stars nearby. SOC grade 3 orbit, 459-year period. Argyle: "It was used by William Herschel in 1803 to demonstrate that pairs of stars are genuinely connected by a mutual force of gravity."
07h 34m 35.86s +31° 53' 17.8" P.A. 51.00 sep 5.4 mag 1.93,2.97 Sp A1V+A4Vm dist. 15.6 pc (50.89 l.y.)
08h 12m 12.79s +17° 38' 51.2" P.A. 349.00 sep 1.1 mag 5.30,6.25 Sp F8V dist. 25.08 pc (81.81 l.y.)
STF 1268 AB: 80; 48x: Iota Cnc. Gold and blue, wide, lovely. Discovered first by Mayer in 1777, then Herschel in 1782. Might not be binary due to parallax difference.
STF 1321 AB: 80; 48x: Faint, equal pair, wide. 7.79/7.88, 14". Tentative orbit published, and both stars might be exoplanet hosts.
STF 1334 AB: 80; 140x: !! Very fine close split, large delta. A Herschel discovery. 3.92/6.09 2.6"
STF 1424 AB: 80; 140x: Orange 2 Dm, good split. Herschel discovery. 2.37/3.64 4.7".
