28 february 2021

Last night was forecast to be clear and transparent, but as seems typical there was a rather thick haze, likely just an accumulation of moisture in the bowl of the Bay Area, which hindered observation of fainter stars.  Seeing was highly variable -- at times I had quite good seeing and I was able to chase after some challenging short period pairs at full aperture, other periods the seeing was ruined and I had to mask down to 7-inches.  Though, even at full aperture, I kept my apodising mask on to steady the view.  Still, plenty of interesting pairs to look at.  I observed from 7:30pm until 11:30pm, when seeing seemed to take a turn for the worse, and I decided to pack it in, in spite of the forecast cloudiness over the next few days.  I washed my mirror so it was nice to have sparkling clean optics to view through.

BU 555 BC: 508; 1067x: So this is a controversial observation, since Bob Argyle has decided to relegate it to his "Myths and One-Offs" chapter in An Anthology of Visual Double Stars.  However I did observe a notched elongation with a reddish A and bluish B with PA to the NNE-NE, slight but noticeable magnitude difference.  This happens to come close to the current predicted PA of 55-degrees.  However, the red/blue stack of low-declination stars along a nearly N-S line could also indicate atmospheric dispersion.  So I hope to have the opportunity to observe this again when Rigel is in front of meridian to see whether the PA holds -- however the opportunity to do so will not be until next year since Rigel is past-meridian at sundown now.  Filing this for future reference!

FWIW this is what Burnham says about this pair: "In 1871, while examining Rigel with the 6-inch, I suspected an elongation of the companion, and called attention of observers with larger instruments to this star.  In 1878 I examined it very carefully with the 18.5-inch, and saw and measured what I felt certain was a real and measurable elongation of the small star.  The measured distances were noted at the time as being too large.  When on Mt. Hamilton with the 6-inch, in 1879, I again measured the position angle, and regarded the elongation as not due to atmospheric causes.  This star was scrutinized with the 18.5-inch at Chicago a number of times from 1880 to 1882, but at all times it appeared either round or very doubtful,  in 1880 and 1890 it was certainly single with the 36-inch with the highest powers under the very best conditions.  If the distance had been as much as 0.05", it would have been noticed on some of these occasions with the large refractor."  Appendix: "This pair may have a period less than that of any known binary....The measures can be represented by a period of about five years, but upon any assumption the elongation should have been seen at some of the times when it was noted as single by apertures large enough to show it.  If it is carefully watched with the largest telescopes, as it doubtless will be, the approximate period will be determined with a few years."

05h 14m 32.27s -08° 12' 05.9" P.A. 30.00 sep 0.1 mag 7.50,7.60 Sp B9 dist. 264.55 pc (862.96 l.y.)

BU 552 AB: 508; 533x: Light yellow A and light orange B, well separated when seeing stills and the stars form airy disks, short period pair with a 97.7 year period.  This will continue increasing to apastron in 2030 and beyond, though the PA will remain about the same -- I think in the future it will be splittable in lower magnifications, which is how I would notice any change. 

Burnham writes: "This pair was discovered with the 18.5-inch, but in looking over the old observing books used with the 6-inch, I find that on December 14, 1874, this star was noted as 'possibly a close pair'…There seems to be something singular about the appearance and difficulty of this pair at times with larger apertures.  It was not noted as difficult at the time of the observation in 1877.  in 1890 it was a hard star with the 36-inch and on two nights in 1892, under favorable conditions, I failed to see it double at all."  

04h 51m 49.92s +13° 39' 18.7" P.A. 274.00 sep 0.8 mag 6.41,8.89 Sp dF6 dist. 40.72 pc (132.83 l.y.) 

COU2031 AB: 508; 1067x: A badly misshaped star, elongated, SSE PA, but nothing really clear, very small scale.  Physical with a 20.58 year period, it will close to periastron rapidly in the next 5 years, and really not be detectible visually until it returns to apastron in the late 2030s.

04h 46m 26.92s +42° 20' 54.2" P.A. 150.00 sep 0.2 mag 6.90,7.80 Sp G0 dist. 67.07 pc (218.78 l.y.)

BU 1047 BC: 508; 667x: Component of STF 645.  Awesome flex on Struve.  Near equal BC stars suspected at 533x, hairline split at 667x.  A really fine little blue pair near bright white A.  Physical with a 32.1-year period, it is at apastron now and will get impossibly close in the 2030s, becoming visually detectible again in the later part of that decade.  Burnham discovered in 1889 with the Lick 36-inch, and recorded 0.4" separation.

05h 09m 45.44s +28° 02' 01.6" P.A. 73.60 sep 0.3 mag 9.11,9.71 Sp dG7 dist. 73.91 pc (241.09 l.y.)

COU 772 AB: 508; 667x: A most excellent, barest hairline split of white stars with significant magnitude.  Suspected with 333x, needed 667x for a clean view.  Very nice.
07h 47m 07.07s +18° 47' 19.2" P.A. 75.00 sep 0.3 mag 8.98,9.17 Sp A0 dist. 621.12 pc (2026.09 l.y.)

AGC 2 AB: 508; 533x: Light orange-yellow A, B is very fine, almost 3 delta mag, nearly 1", very nice pair
07h 47m 58.47s +28° 40' 02.7" P.A. 116.00 sep 1.0 mag 7.76,9.73 Sp G8III dist. 194.17 pc (633.38 l.y.)

WRH 15 AB: 508; 1067x:  82 Gem. I see an elongated misshape, PA to the NNE, but not firm.  Physical with a 580-year period.  R.H. Wilson, 

07h 48m 33.65s +23° 08' 27.5" P.A. 24.50 sep 0.3 mag 6.85,7.30 Sp G2III+A4V dist. 241.55 pc (787.94 l.y.)

STF1162 AB: 178; 205x: Seeing suddenly ruined so masked down to 7-inch.  Pretty light yellow A and blue B, wide, around 2 delta mag. 
07h 57m 22.66s +13° 12' 24.7" P.A. 327.00 sep 9.0 mag 8.00,10.17 Sp G5

STF1170 AB: 178; 205x: Lovely close split, white stars, near equal
07h 59m 45.52s +13° 41' 19.9" P.A. 108.00 sep 2.4 mag 8.74,9.09 Sp F5

A 2954 AB: 178; 205x: Hairline split with seeing, significant magnitude difference, white stars.
08h 00m 27.88s +09° 54' 49.0" P.A. 338.00 sep 0.6 mag 8.42,8.98 Sp F8

STF1171 AB: 178; 205x: Very tough for a Struve.  B is very faint and comes to view only with seeing as a very fine point, pretty well separated from A, but A needs to be a disk for B to resolve out of the diffraction.  Seen fleetingly, somewhat better with averted vision but averted vision often misses moments of best seeing.  Physical.
08h 01m 00.78s +23° 34' 59.2" P.A. 326.00 sep 2.0 mag 6.48,9.95 Sp K1III-IV dist. 87.95 pc (286.89 l.y.)

STT 186 AB: 178; 205x: Beautiful hairline split, white stars, around 1 delta mag and 1".  Great pair. 
08h 03m 18.52s +26° 16' 03.5" P.A. 75.00 sep 1.1 mag 7.71,7.93 Sp A4V dist. 188.32 pc (614.3 l.y.)

STF1177 AB: 178; 205x: Excellent, around 1 delta mag and wide, blue-white stars, nicely resolved.
08h 05m 37.06s +27° 31' 46.9" P.A. 350.00 sep 3.5 mag 6.69,7.41 Sp B9V dist. 294.12 pc (959.42 l.y.)

STF1186 AB: 178; 205x: Really nice, very large delta mag of about 3, about 3", white stars, large round disk for the A star and tiny point for B. 

08h 08m 49.61s +27° 28' 49.4" P.A. 212.00 sep 3.3 mag 7.06,10.08 Sp G8III-IV dist. 229.89 pc (749.9 l.y.)

STF1187 AB: 178; 205x: White stars, a little more than 1 delta mag, wide about 4".  Physical with a 1385.156-year period.
08h 09m 30.45s +32° 13' 18.8" P.A. 19.50 sep 3.0 mag 7.19,7.98 Sp F2 dist. 64.68 pc (210.99 l.y.)

STF1195 AB: 178; 205x: Both stars are faint, B seen well because it's widely separated about 8", about 2 delta mag.  Physical.
08h 12m 38.45s +30° 27' 33.3" P.A. 333.00 sep 9.2 mag 9.29,11.80 Sp G

STF1197 AB: 178; 205x: Fine pair of white stars, around 2" and 1 delta mag.
08h 12m 44.45s +29° 32' 30.9" P.A. 101.00 sep 1.8 mag 9.01,9.67 Sp A2 dist. 398.41 pc (1299.61 l.y.)

STF1212 AB: 178; 205x: 1 delta mag, fairly well split, nothing special but still a pretty pair.  Not physical.
08h 18m 03.47s +30° 49' 56.0" P.A. 241.00 sep 5.5 mag 8.63,10.10 Sp F2

A 2961 AB: 178; 205x: A is a light orange star, B is a very exceptionally fine point just a little more than 1" separation, sharp with seeing, 3 delta mag.
08h 23m 55.20s +10° 37' 55.4" P.A. 267.00 sep 1.3 mag 6.34,9.42 Sp M2III dist. 272.48 pc (888.83 l.y.)

A 1746 BC: 508; 1067x: Component of STF1224.  I see a very subtle notched elongation, PA SSW, noticeable mag difference.  Physical with a 21.78-year period, it is a nearly circular orbit and near periastron, it's apastron will be in 2029 at 0.16"
08h 26m 39.82s +24° 32' 03.7" P.A. 199.10 sep 0.1 mag 8.50,8.50 Sp F7V dist. 79.74 pc (260.11 l.y.)

STF1223 AB: 508; 205x: Bright white, equal, wide -- dramatic but not much.  Not physical
08h 26m 47.08s +26° 56' 07.8" P.A. 219.00 sep 5.2 mag 6.16,6.21 Sp A3V+A6V dist. 84.53 pc (275.74 l.y.)

STF1228 AB: 508; 205x: Bright white, 1 delta, wide
08h 27m 39.04s +27° 33' 42.5" P.A. 352.00 sep 9.0 mag 8.87,9.68 Sp F2 dist. 157.73 pc (514.52 l.y.)

HU 714 Ba-Bb: 508; 533x: Nicely split with seeing, 0.5-1.0 delta mag, 0.5" separation.  Short period of 195.5 years, it is at apastron now and will remain there the rest of my lifetime.
08h 26m 56.47s +32° 11' 47.3" P.A. 313.00 sep 0.8 mag 9.77,10.07 Sp K2 dist. 57.8 pc (188.54 l.y.)

HU 717 AB: 508; 533x: Exceptionally finely split with 333x, steady clean split with 533x, near equal white stars.
08h 32m 34.65s +32° 27' 25.1" P.A. 52.00 sep 0.5 mag 9.71,9.47 Sp G0