10 august 2021

Was able to spend some time with the 6-inch last night, the seeing being too average for the 20.  But still some pretty difficult pairs seen.

STF 2570 AB-C: 152; 175x: Light orange A and blue B, nice separation, 2 delta mag.  AB is AGC 10, 0.2" 8.43/8.42
19h 44m 56.78s +10° 46' 30.6" P.A. 277.00 sep 4.3 mag 7.62,9.81 Sp B3IV-V dist. 170.94 pc (557.61 l.y.)

STF 2562 AB: 152; 175x: Easy wide light yellow A and 1 delta mag blue B.  WDS says physical but no orbit yet.  These are likely gravitationally bound: 48% parallax range overlap, 1,660 AU separation, and the radial velocity is less than the escape velocity.
19h 42m 45.86s +08° 22' 57.5" P.A. 251.00 sep 27.2 mag 6.95,8.69 Sp F8V+G0V dist. 66.45 pc (216.76 l.y.)

STF 2543 AB: 152; 175x: Light orange A and much fainter, wide B, just seen with direct vision.  WDS uncertain but these do not share any parallax, so they are not.
19h 36m 12.61s +06° 00' 26.7" P.A. 151.00 sep 11.5 mag 6.76,10.45 Sp G8III dist. 201.61 pc (657.65 l.y.)

BU 139 AB: 152; 456x: Very subtle notched unequal elongation at all powers.  Physical with a 587-year period, currently coming of apastron, it will continue to tighten.  Component of STT 177.  Burnham discovered with his 6-inch in at 0.5", about what it is now, an astounding catch.
19h 12m 34.45s +16° 50' 47.2" P.A. 135.80 sep 0.6 mag 7.11,7.95 Sp B9IV dist. 242.72 pc (791.75 l.y.)

HO 91 AB: 152; 175x: Very pretty light orange A, wide faint B. FF Aql.
18h 58m 14.75s +17° 21' 39.4" P.A. 146.00 sep 7.0 mag 5.44,10.12 Sp F8II dist. 473.93 pc (1545.96 l.y.)

STF 2540 AB: 152; 175x: White A and very light orange, 2 delta mag B, off of the Coat hanger asterism. WDS uncertain, however they do not share the same parallax range.
19h 33m 17.05s +20° 24' 50.5" P.A. 145.00 sep 5.4 mag 7.52,9.23 Sp A3 dist. 152.67 pc (498.01 l.y.)

STF 2504 AB: 152; 175x: Light yellow A and light blue B, wide 2 delta mag.  WDS uncertain, but there is a good chance they are gravitationally bound: 13% parallax range overlap, 542 AU separation, and stellar mass of 1.57/0.97.
19h 20m 59.85s +19° 08' 43.4" P.A. 282.00 sep 8.6 mag 7.00,9.03 Sp F5V dist. 62.7 pc (204.53 l.y.)

STF 2523 AB: 152; 175x: Equal white stars, well separated.  WDS says physical, however they do not share the same parallax ranges, so they are not.
19h 26m 48.38s +21° 09' 46.2" P.A. 148.00 sep 6.3 mag 7.95,8.05 Sp B3V+B7V dist. 1470.59 pc 
(4797.06 l.y.)

BU 248 AB: 152; 245x: 2 Vul. Nice!  B seen just outside bright A's diffraction as a very small fine point, 3 delta mag.   WDS is uncertain, but there's a good chance they are gravitationally bound: 24% parallax range overlap, 985 AU separation, 6.47/2.98 mass.
19h 17m 43.64s +23° 01' 32.0" P.A. 128.00 sep 1.8 mag 5.43,8.75 Sp B0.5IV dist. 373.13 pc (1217.15 l.y.)

STF 2727 AB: 152; 175x: Gam2 Del.  Gorgeous, light yellow-orange A and blue-green B, I like this better than Albireo.  Physical with 3249-year period, it will slowly tighten the next couple of hundred years.
20h 46m 39.50s +16° 07' 27.4" P.A. 264.70 sep 8.9 mag 4.36,5.03 Sp K1IV+F7V dist. 38.73 pc (126.34 l.y.)

BU 681 AB: 152; 175x: ! What a difficult pair.  Did not get a convincing view at higher powers, though there seemed a brightening in diffraction with averted vision.  Going to 175x I saw the B star and an especially fine point cleanly separated.  WDS says physical, but very disappointingly they do not overlap their parallax ranges.  Burnham discovered with the Dearborn 18.5-inch, at 2.5"
21h 13m 16.58s +16° 55' 08.4" P.A. 243.00 sep 2.8 mag 7.48,10.92 Sp K3III dist. 213.68 pc (697.02 l.y.)

BU 74 AB: 152; 245x: Very minute and faint B just within A's diffraction.  Discovered with 6-inch at 
1.5".  WDS uncertain, there is no EDR3 data for the B star.
21h 35m 11.99s +21° 24' 14.9" P.A. 338.00 sep 1.0 mag 7.45,9.05 Sp F5V dist. 85.18 pc (277.86 l.y.)

STF 2799 AB: 152; 175x: Very nice near equal yellow-white stars, closely separated, near M15.  WDS uncertain, their parallax ranges do not overlap.
21h 28m 52.79s +11° 05' 05.2" P.A. 258.10 sep 1.9 mag 7.37,7.44 Sp F4V dist. 105.04 pc (342.64 l.y.)

BU 163 AB: 152; 245x: B is just detectable, very, very faint, tangent to or touching A.   Physical with a 78.54-year period, it is at apastron and will remain there for another 20 years before making a rapid closure.
21h 18m 34.85s +11° 34' 08.2" P.A. 77.10 sep 0.9 mag 7.31,8.88 Sp G0V+G6V dist. 47.66 pc (155.47 l.y.)