R1 Measurements rejected by the sigma-clipping algorithm. These observations R1 were discrepant by more than four times the standard deviation of the R1 residuals. R2 We removed the observations by G. M. Searle in 1866.93 and 1867.03 R2 (1888AnHar..13...17W). As described in the table remarks, these R2 observations do not refer to the "usual" companion (Sirius B), R2 but are probably a false image. R3 The HST observations by Schroeder et al. (2000AJ....119..906S) were R3 re-analyzed in the current paper. These measurements have been replaced by R3 the revised values published by Bond et al. (2017ApJ...840...70B). C1 Otto Struve corrected his measurements for systematic errors by C1 measuring artificial double stars. He provided both the original and C1 corrected measures of the separation and position angle for the C1 companion of Sirius (Struve 1893, Pulkova Obs. 10). Aitken (1918, C1 The Binary Stars, New York: D. C. McMurtie, 60-61) cautions that the C1 variance of the angles and distances compared with other observers is C1 often larger for Struve's corrected values. However in the case of C1 Struve's measurements of the companion of Sirius, we found that the C1 mean residuals in the position angle improved when using the corrected C1 values, while the residuals in separation did not change significantly, C1 so we opted to use the corrected values. C2 Struve (1893, Pulkova Obs. 10) lists a measurement of Sirius in 1861.21. C2 However, this predates the discovery of the companion Sirius B by A. C2 Clark and his son on 1962 Jan 31 and the first formal measurement by C2 G. P. Bond on 1862 February 7. Comparing the uncorrected PA and separation C2 in Struve's table in 1893 with the measurements published by Struve C2 (1864MNRAS..24..149S), we suspect that 1861.21 is a typo and should refer C2 to the observation on 1863-Mar-16. C3 For the photographic observations by Lindenblad (1970AJ.....75..841L, C3 1973AJ.....78..205L), tables are given for the raw individual measures, C3 while only the mean measures are corrected for emulsion contraction. C3 The average time span covered by these mean measures is ~70 nights, so we C3 used Lindenblad's tabulated scale corrections to compute corrected C3 separations and position angles for the individual measurements. We then C3 took the mean for plates taken on the same night, reducing the number of C3 individual measurements from 157 down to 77 measurements on unique dates. C4 For the 1904.186 measuremment by T. Lewis (1905MNRAS..66...17L), C4 the title of the article, text, and first page of the data table all C4 refer to observations taken in 1904. Subsequent pages of the data C4 table (including the page that Sirius is listed on) list an epoch of C4 1903. However, this is probably a typo, so we have corrected the date C4 to be in 1904. M1 Mean position computed for multiple measurements on a single night. M1 This mean is not reported in the original publication. M2 Only the mean position across multiple nights was reported in the M2 original publication. M3 Measure cited in a compilation of measurements by different observers. N1 The separation for the 1862.275 measurement by Lassell is reported as N1 4.92 arcsec. This is clearly incorrect and not consistent with N1 measurements by other observers. The Washington Double Star catalog N1 assumed a factor of two error had been made in reporting the separation N1 and list the separation as 9.84 arcsec. N2 Observations rejected by the sigma clipping algorithm that were noted N2 in the original publication as uncertain or obtained under bad N2 conditions. N2 - Secchi 1863.15 - Secchi notes the observation is "incerta" and marks N2 the separation with a question mark. N2 - Eastman 1867.293 - "Sirius quite unsteady. Companion occasionally N2 invisible." N2 - Bruhns 1868.254 - "schlect" N2 - Struve 1879.19 - "Im. tres tremblantes et diff." N2 - Struve 1886.21 - "Extremement difficle." N2 - Lewis 1898.214 - "diffused image at low altitude" N2 - Brown 1899.210 - "poor" N2 - See 1899.755 and 1899.818 - observations are listed as "doubtful" and N2 "uncertain," and the values are quoted in brackets. N2 - van den Bos 1941.082 - PA and separation listed with question marks N3 In the table of observations, Secchi (1866AN.....68...87.), N3 reports the combined position measured by Secchi and Struve in N3 1865.225 using the same instrument. We report the position measured N3 only by Secchi which is given as a footnote to the table. N4 The aperture size for the Gledhill observations in 1880.04 and 1881.16 N4 was not known from the literature. We set the aperture to 0.2 m for N4 scaling the uncertainties during the orbit fit. N5 For the 1882.988 measurement by Burnham, S. W., the PA is listed as N5 41.6 deg in Burnham (1883MmRAS..47..167B) and as 40.6 deg N5 in Burnham (1883MNRAS..43..318B). N6 Separation listed in brackets or parentheses in original publication N6 but not rejected by fit: N6 - Young 1884.929 - separation listed in brackets N6 - Rabe 1914.81 - separation listed in parentheses with colon N6 - Barnard 1915.963 - separation listed in brackets N6 - Aitken 1927.178 - separation listed in parentheses N6 - Finsen 1929.041 - separation listed in parentheses - "Wires suspected N6 of fiddling, distance measure rejected." N7 Many of the recovery observations of Sirius B following the periastron N7 passage after 1890 are doubtful. The recovery observations made by N7 See, Douglass, and Cogshall at Lowell Observatory from 1896.668 - N7 1896.695 and reported by T. J. J. See (1896AJ.....17....1S) N7 were taken in the morning shortly before sunrise when Sirius was low N7 in the sky. See notes that the mean position angle of 220 degrees at N7 a separation of 5.10 arcsec is about 30 degrees behind its predicted N7 location and the separation is larger than expected based on the N7 previous orbit fit. Robert G. Aitken and J. M. Schaeberle N7 (1896PASP....8..314A, 1897AJ.....17...76S) reported measurements N7 between 1896.814 - 1897.027 made from Lick Observatory at a N7 significantly different mean position angle of 189 degrees and a N7 separation of 3.7 arcsec. Both Aitken and Schaeberle comment that N7 neither of them saw a star at the position reported by Dr. See. N7 Following the contradictory reports, Stimson J. Brown N7 (1896AJ.....17...46B) published observations from his logbook that N7 were taken earlier in March 1896 at the U.S. Naval Observatory. The N7 position angle is similar to the values reported by Aitken, but the N7 separation is about 1 arcsec larger. Brown notes that the observations N7 were taken under challenging conditions and he did not have much N7 confidence in their reliability. See (1897AJ.....18...75S) N7 later refuted his earlier measurements after unsuccessfully searching N7 for the companion while observing from Mexico and then successfully N7 detecting the companion at a position angle of 175 deg and separation N7 of 4.6 arcsec in September 1897 at Lowell. He writes, "The erroneous N7 conclusion to which I was led last year seems to have arisen from a N7 very unusual and entirely unexpected cause, of which we need not speak N7 here..." In hindsight, See also reported in that publication, two N7 observations from April 1895 that he initially did not think were N7 worthy of announcing. The difficulty in attempting to find Sirius B N7 using the Lick Observatory 36 inch in February and March of 1896 was N7 described by William J. Hussey (1896) (1896PASP....8..183H). N8 The observations by Brown (1900AN....152..329B) in 1899.210 and N8 See (1900AN....153...99S) in 1900.248 - 1900.319 were originally N8 published by the respective observers and republished with slightly N8 different values in a later publication of the USNO N8 (1911PUSNO...6A.115). According to the USNO publication (page A LXVI), N8 "All of the observations have been thoroughly checked. A number of N8 errors were discovered in the earlier reductions and corrected. N8 These reductions have also been slighty changed by the adoption of N8 a later and better determined value of a revolution of the micrometer N8 screw. This will account for small discrepanacies between the results N8 published here and those previously published in the astronomical N8 periodicals." We report the updated 1911 values. N9 van Albada (1962JO.....45....1V), published photographic N9 positions of Sirius B. Except for the first two observations in N9 1955, these positions were corrected for emulsion contraction in N9 van Albada (1971A&A....11..317V). We report the N9 corrected positions. N10 Jasinta & Hidayat (1999A&AS..136..293J) did not correct these N10 epochs for emulsion contraction. For all other dates, we used the N10 corrected separations. U1 Bond (1862AN.....57..131B) reports that Mr. Clark discovered U1 a companion to Sirius on the evening of 1862 Jan 31 using a telescope U1 with an aperture of 18.5 inches. U2 Hussey (1896PASP....8..183H) attempted to resolve Sirius on U2 five nights in February and March of 1896 using the 36 inch at U2 Lick Observatory but was unsuccessful. U3 G. C. Comstock (1906odse.book.....C) attempted to resolve U3 Sirius on two nights in 1903 using the 40 cm equatorial at U3 Washburn Observatory but was unsuccessful. U4 H. M. Jeffers was unsuccessful at resolving Sirius B on four attempts U4 in 1945-1950 using a micrometer on the 36 inch at Lick Observatory. U4 He did not publish these observations, but they were included in the U4 complete IDS list transferred to USNO in 1964. U5 S. Archer (1958JBAA...68...95.) was unable to resolve Sirius in 1957.16.