CIHM Microfiche Series (Monographs) ICMH Collection de microfiches (monographies) Canadian Institute for Historical Microroproductians / Instltut canadien de microreproductions historiques 1^99 Technical and Bibliographic Notes / Notes techniques et bibliographiques Tno has r-'ilempted to obtain the best original re;--' r.yaiiaol' for filling. Features of this copy which 'r>v' ;'*■- fc^t'ioqraphicaily unique, which may alter any of the .i;idJ'=;. in the reproduction, or which may significaniiy c.iange the usual method of filming are checked belov. n Coloured covers / Couverture de couleur I I Covers damaged / Couverture endommagee □ Covers restored and/or laminated / Couverture restauree et/ou pellicuiee Cover title missing / Le titre de couvenure manque I I Coloured maps / Cartes geographiques en couleur □ Coloured ink (i.e. other than blue or black) / Encre de couleur (i.e. autre que bleue ou noire) □ Coloured plates and/or illustrations / Planches el/ou illustrations en couleur Bound with other material / Relie avec d'autres docume '3 Only edition available / Seule edition dispcnible Tight binding may cause shadows or distoriicr, cleg interior margin / La reliure serree peut causer ce I'ombre ou tie la distcrsion le long de la rriarce interieu'e. Blank leaves added during restorations may a-pesr within the text. Whenever possible, these have ceen omitted from filming / II se peutquecertames caces blanches ajoutees lors d'une restauraiicn apparaissenl dans le lexte, mais, lorsque cea e'5 t possible, ces pages n'ont pas ete filmees. D L'Institut a micrjfilme le meilleur exemplaire qu'il lui a ete possible de se procurer. Les details de cet exem- plaire qui sont peut-etre uniques du point de vue bibli- ographique, qui peuvent modifier una image reproduite, ou qui peuvent exiger une modification dans la metho- de normale de filmage sont indiques ci-dessous. Coloured pages / Pages de couleur j Pages damaged/ Pages endommagees I / Additional comiments / Pages restored and/or laminated / Pages restaurees et/ou pelliculees Pages discoloured, stained or foxed / Pages decolorees, tachetees ou piquees D \2f Pages detached / Pages detachees sA Showthrough / Transparence I I Quality of print varies/ n D D Qualite inegale de I'impression Includes supplementary material / Comprend du materiel supplementaire Pages wholly or partially obscured by errata slips, tissues, etc., have been refilmed to ens'.jre the best possible image / Les pages totalement ou paniellement obscurcies par un feuiliet d'errata, une pelure, etc., ont ete filmees a nouveau de fa^on a obtenir la meilleure image possible. Opposing pages with varying colouration or discolourations are filmed twice to ensure the best possible image / Les pages s'opposant ayant des colorations variables ou des decolorations sont filmees deux fois afm d'oblemr la meilleure image possible. Continuous pagination. Commenlaires supplementaires: This itpm is tilmcd al ihp rs ducticn rslio checked below / Ce document e&l dime au laux dc reduction indique Ci-deisout. 10x 14x 18x 22x 26x 30x 1 i 1 1 / / 12x 16x 20x 24x 28x 32x The copy filmed here has been reproduced thanks to the generosity of: D.B. Weldon Library University of Western Ontario L'exemplaire filmA fut reproduit grace i la g^nArositA de: D.B. Weldon Library University of Western Ontario The images appearing here sra the best quality possible considering the condition end legibility of the original copy and in keeping with the filming contract specifications. Les images suivantas ont iti reproduites avec le plus grand soin, compte tenu de la condition at de la nettet4 de l'exemplaire film*, et en conformity avec les conditions du contrat de filmage. Criginel copies in printed paper covers are filmed beginning with the front cover and ending on the last page with a printed or illustrated impres- sion, or the back cover when appropriate. All other original copies are filmed beginning on the first page with a printed or illustrated impres- sion, and ending on the last page with a printed or iJluatrated impression. Les e^emolaires originaux dont la couverture en pap est imprimAe sont filmis en commandant par le premier plat et en termlnant soit par la derniAre page qui comporte une empreinte d'impression ou d'illustration. soit par lu second plat, salon le cas. Tous les autres exemplaires originaux sont filmAs en commenpan'i par la premiere page qui comporte une empreinte d'impression ou d'illustration et en terminant par la derniAre page qui comporte une telle empreinte. The last recorded frame on each microfiche shall contain the symbol — ^^ (meening "CON- TINUED "I. or the symbol V Imeaning "END "). vhichever applies. Un des symboles suivants apparaftra sur la derniAre image de cheque microfiche, selon le cas: le symbole -^ signifie "A SUIVRE". le symbole V signifie "FIN ". Meps, plates, charts, etc., may be filmed at diffei-ent reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, pisnches, tableaux, etc., peuvent etre filmis A des taux de reduction diffirents. Lorsque le document est trop grand pour dtre reproduit en un seul cliche, il est film^ d partir de Tangle supArieur gauche, de gauche d droite. et de haut en bas, en prenant le nombre d'imagas nAcessaire. Les diagrammes suivants illustrent la mAthode. 1 2 3 1 2 3 4 5 6 PObC 4 K DEPARTMENT OF THE INTERIOR CANADA Deputy Mini.iter. PUBLICATIONS OF THE Dominion Observatory OTTAWA W. F. Kmo. CM.G., LL.D. Ciretter. Vol. Ill, No. 4 Orbit of the Spectroscopic Binary A Bootis i 5 « '.3 •I |'» REYNOLD K. YOl NG, Ph. D. OTTAWA 'ioVKUNMKNT I'UI.MIN,; lilUKAr lUlO 88893—1 The binary character of A Boutis (a = 14'' 14'". 5=+35°54', tyi)e Go, mag. 4S) was announced by Moore in Lick Observatory Bulletin 12:}. Forty-two spectrograms secured at this observatory with a one-prism speotro- grapli have been u.sed in determining an orbii. In this, as in many other cases, the Lick Ob.servatory results have been useful in defining tiie period. The details of their observations were very kindly communicated by mail. In general an orbit of a late type star determined with a. one-prism instrument does not compare favourably with an orbit of the oame star ba.sed on three-pri.sm results. The accuracy is so much greater in the latter ca.^e that the practice has been generally followed of leaving the late tyi)es for high dis])ersion. However, the range of the present binary permits of a fairly accurate determination of the orbit with ;i one-pri.sm uistrument. On this account and al.-^o because at the time the number of available binaries was rather limited, the star was i)laced on the observing |)rogranun(> here. ^^1 ORBIT OF TIIK SPECTROSCOPIC BINARY A BOOTIS. BV UEY.NULD K. YOLNG. Pli.D. Table I gives the wave-leng»hs of the lines used in reducing the measures. The corrections in the third column are comi)uted to make the sun; of the weighted residuals of column four vanish. '{"he residuals were taken in the sense, ()i)served minus the mean of the plate. If we comi)ute from Rowland's Preliminary Table of Solar Wave-Lengths the lines which would in one-prism disi)ersion lie near tlie,>e. we lind that tlii' wave-length> uiveii in the table are about (»•():} Angstrom units larger The method of combining tlie various lines in a high disju-rsion tabh' is arbitrary and the resulting jiosition of the tilend uncertain. .\l).,ut all we may say of the wave-lengths given, is that they arc homogeneous anil that tin scale IS si' n i 5 96 in Bl.U A'lIDNS OK rilK Dd.MlMi'N ( )BSKHVA lOKY. not very (litTcrciil from Howlaiurs. It is douhtful if tiicy would suit unotluT star unless it were exactly the same tyju'. The results from several late type stars, whose orbits have heeii eoiuiiuted at tlus observatory, seem to show that the apiuireiit wave-leiijiths of blends, as measured on low (lisi)ersion i)lates, vary markedly with u slight variation in the speetral type. The usual method of first finding approximate elemeiUs and then eorreelin^ these ditTerent ially was followed. One eorreeticni was found sulheient. The sueeessive steps in the solution and the results are given below. In the radial velocity curve the initial date is Julian Day 2,420,r>0(). •lAHl.K 1 1 1 1 Alfifhraic Arillinii'tir Number of i:icmi-nt \\ :ivr-l.cn(llli. ( 'nrri'iMinii U.siJuiil Ki^iilii;.! tmu'S MwiMircii Fe ii)0."p-4jri - ■o;i7 i - 2'8 11 24 Fe 4(t4.'i '.175 + 011 + 0-8 IS 4 Fe 4IHi:i 7.nl'. -h 114 + »'4 8'4 ' 4 Fe 41171 ',!;('• - IK>4 1 - 0-3 2-7 10 Fe + 4(WJ-7:i7 -■02:i - 1-7 1 4 1 30 y till) t)4;i + 041 + 3 '• .'i U 16 /■■, - T: 41'j;i74s + (t:i'3 + 2^4 1 4 7 13 Fc 4i-,i7yi -r 021 + \r. 3-3 22 Fe 4i'.n i.it7 -1- oil + OS ' 3 3 20 Fe iM)2-2'M - o;!2 - 2-3 ;') 2 33 Fe 4J;it) (».'i7 + -oi;i + 0-9 4 3 17 Fe 4J.")() liHl - oi;i - 9 3 3 -29 Fr \2:>^a):> - 010 - 7 1 .5 6 fi- 4J71SJ'.) rWXi + 0-4 3 1 40 4J7.i ll'.» -003 - 0-2 3 3 18 t\ - T, 4'JS'2-7J'J ^•027 + 1-9 4 2 36 Ci 4:v.t 7f.r, ^ tHH + 0-2 3(1 34 r. 4;ii4 Miti -010 - 7 1 II 30 4:t2;M)iJ + 073 + 4-S 7 1 15 Fe 4:(2.">-7(l2 1 - (MS - 0-2 4 S 12 Fe 44U4 S'.H) 1 -004 - 0-3 1 37 Fr 441.") Ji.'i 1 +007 + 0-5 3'.t 40 Fe 44;i()-4tm - 023 - 16 3 7 35 Fe-Mn 14112 ii:t7 -029 - 2 1 li 27 Fe-T< 4"ii'.t :iv> + 015 + 10 4 1 33 Cr-r, I."i7l S'.ll -•000 t - 0-6 13 39 OHBIT OK THK S1'K( TK<)S( ( )1'I( ' UlNAKV A UilOTI>. 97 LICK AND I'OTSUAiM OUSKRVATIONS. (Jl)scrv:iti>ry .IiiliMli Day. Phas<' from J. I). 2,420,.WO Vcluctv ■ () ('. Li.-k, Lit-k Lick Lick, 2.417,302-S-2IJ 7.017-99S 7,004-970 7,087-924 7,725-799 8,818-46 8,839-39 9,572-38 i 254-92 85-30 132-28 155-23 193- !u 14-00 34 99 132- 13 -39 11 -10 -12 -IS -23 -32 8 1 3 '' 3 _ •> 1 +4-9 + 5-8 +5-8 Lick. + 5-8 Hotsdam +4-9 Potsdam +8-1 Potsdam +7-3 +3 4 « ••J Si? lit 88893—2} £1& yh I'lUl-UAllDNS or IHK LKJ.MIMUN obSEKVA lOKY. OTTAWA OHSEHVATIONS. 0702 0^2•■| liMill UMI5 I. '.II 11 Tlll'.i 7II.V.I 7011^ 7ll7ii 7I)S.S 7111 71JII 7i:j'.i 7141) 7ir)S aoH 71<.W 7"J'J'^ 7271 7281 72SS 72',n 7:U7 7:tJl 7:iJii 7:nii 7:i."i:i 7:t.v.i (■ '1 •,■1. 17 M,,r 1 War N \\a, 11 Mar HI Mar -M Mar J'.l Vjinl 1 \,,nl 7 \|.nl IJ \|.n! 1 < \|.nl Jll \pril j\ 11 ^ Mav li Ma\ i:t Mav j:i Mav ■J 7 Mav :(i) Jillit' li ,lunv Hi .lllTIr Jll .lui.r 'J 7 .lillv s •lulv -11 .liilv 27 Aut;, ,■> A.ii:. HI Aun. 17 !AUK. 26 ISt.pt 2 Scpl H) S..].. 17 >..l>t 21 S.pt 22 S,.pt 27 S,.pt 2 s 1 )ll :! llrl - 1 In HI ( 1, 1 I'l II, 1 21 Oct. 2;i -40 + SO -46r> + 2 1 -30-H ; + 7-2 -323 - 3h -20H j r Mi -21 -S , - 2-3 -14 + 31) -2S-5 -13-0 -11 4 - 3h -23 1 - S3 -16-7 - 19 -12 2 + 2-4 -12 .'> + 2-3 -I.-. -3 1 00 -12-2 1 + 3-4 -21!t ' - 71-2 -I'.i:) - 2 4 ; -130 + 4 4 -20 t) - 8-4 -12 9 + b-5 -17-4 + 2ti -24() - 3 li -22'. + 1 -2S-4 - 3-7 -22r) + 30 -27-4 + 0-8 -34 - 4-8 -340 - 31 -38-3 - 3 1 -41 3 - 3 -43 2 - 2 ' -431 1 + 4-0 -4S.7 + 10 -51-9 - 0-8 -4S-7 + 1-4 -.-,4 -3 - 40 -47 4 - 3 4 -34-7 1 - 02 -2S(i i + 2 9 -27-9 - 3-4 -17 + 2-5 1 -18 ■" + 0-3 •P.pia«k--ll. ll-IIJirpar; pi»Parker; C Cannon; V ■ VounH (IIU;1T OF THK 8PK(Tli(iSCoiM( HiNAKV \ Boons. 99 MEASl... »i' \ li("''ll> iiJ I i.J If ' ti I >• 100 rrnMCATioNs of thf: dominion obsekvatory. Nn:\sn!i;s oi' a hootis- r,ii,/,iN/.i/, 101.") '.cri tOii:i 751) 1071 '.i:t'i lO'.IJ 7l^ 4111) iit:i iij;i-7.-)i 11 .;7 '.t'.to Ji:f2:i;ti) U'll Mil'. UOJ J'll l.MC. 1I7J r.*.")0 liiii ■tJ71 HJ'.i 1J7.") i:u 4.'vJ-7.'-' IJv.l 7i'iii 4:11 4 Mill 4:il7 4Jrt i:VJ.'> 7'.I2 1101 S'M I in:. JJs 4i:io 'lilt 411.J w\i t.")l'j 7i'.i'. tvivn in>' til \ , It:.di:il l'.')()l Vi'l Wt -■.W,-2 ■ iHo; -J4 :i -■_"• 1 -JJ 1 -J',) '.I -J7 1 -.ill -• Jl :w.7 (1 111 Js \A \Vi js tr. • i:i -' ■ uV - ^-w I 1 -1! 1' - '.Mi 1.") V -10 .■. .') A s .-, 1 u :i 1 1 II' 1 17 (I. V.I. \Vi 111 1 •U) 1 ■■Z2-b ■JO -Jl 4; -J1..1 -!.')>' -Jl 7 -i;s J, -17 J - 17 >' - Jii 10 .'.O 71 07 J^ I. -17 ~ir, r.i -jii (I 11 ij JO :ii J 17 117 JS V.l \Vi -17 a -1:1:! - 4 .'. -H) 4 -11 J -JO -10 i.r -1.-. :!, -IJ.'ij -i:i-:V -11 .") -nij -i;i.7i - 1.") o| 1.'. 7 .'. I -IJ 0' I'l ;; -IS. SI -17 (I -ij ;i: -11 1' -Jl s -i:!.t) ;io J v.-i : Wt j:i n i:t 71 O II, II Js \..| Wt - II". 4- J- 111 - 0-7' -f IJ' T- 1 (11 - S.4 ■I- l-.i + 4 J - 1:1 1.-. 1 S 17 J i (I I'l JS - (in + l).SI - 4 ..5; - S-jl - n.7i v.l, Wt -i:i - 1! - (i ■ - 11- - S- - 4 - 4 :ii ! - l-fi - 6-1 - --a + 2-8l ,1.() - fi. - l-o' , i-o! - (i-7; -ijo; t- J 1. - 4.Jj - O.4J - 70' - ()..") 1 + .^7 - "^ .2 - H-T - 7H 01 JS 1 10 J! (I (I. J' OHBIV OK THK SI>E( IROSroPIC BINAUY A BOOTIS. 101 MEASURES OK A HOOTIS-fv.,,/,,,,,,,/. (()();!• 75(j 11)71 (lUil 10'.IJ7ls lUliillH ll.'H-7.-.l ll.'7 !)!MI tiiil s(«; IJOJ 2'.ll l.':iil()72 (-•.'.() ()1() t.'71 s.'ii IJ7.-, l.il IJS2 7JJ lJS!t-7tit) CtMSCii i;tl7 IJll t:).':i-7!IJ tldl S(IO I i:iO .■.():! •titlj IMI'J Itmtl: \.lu,■,t^ V.'l. W , t- t J + SO t ."l 1 1 + or 1 - l-S! + I ti^ - (t:t! 1 t."il',l 7iii) + li :. i:.7i s'li *~ ■rs' i Wriglitiil nil an (1 tr> V, 1.' ill \j 11 117 Curv. JS ITBI.ICATIONS ri!r,> III' s liodTi.- d'hiiiiiiii. llKI."i IJI'i 1071 :>-V.> 4()itJ Tls trj;t 7.'.4 4rj7'.m() 4i:iJ :t:!ii 41'.M s(tti 4.'0-J J'.il 1JJ1MI7J lJ.",o r.ir, 4J71 S."l tJ7:i i.ii 4.'v.' 7JJ 4.'VI 7liii 4;U7 IJi, 4;vj:. 7'.rj 41(11 VKI 411.". JJv 4i:!ii .'.(i:! l.M'. 7h., i;i7l v'U \V. iclitrM V.l \Vt •4 1 V.l \Vi - ltd' J I'. .nil V. \. Ciirv. Ha.lM,l V,l...iiv r - 1 V 1 _ 11 s I - :i .' 1 _ .'i 1 _ :t-7 1 _ OH i - hi 5 - t)-| » _ S-7 ! - ■i:! 1 + OS 1 - 4 2 1 - H-H i i 1 :f ! ' •J r i 1 ^7 It". - 4( - 1 - :i- + :>■ - 24-5« I :.i jn i,ti II I'l II js •as* \ .1 w t -lOli t II 11 ."1 II '^ ■ - ,i I. ; 17 1. 1 - ;i 4| 1 - •i-3j i -i:iu| i - iiol ! - (■,..■,! s - (iiti S II I'l \,1 \Vi 11 1 1 '1 STi - 4-S; - :t-sl + 4-S + 0. - 3 4 + J 9-1 4 fl ■X' .'S? \il \Vt 10 7 t 111 \ ) :i :t n; \il Wl ■ (l-Ol - s-r>! - r,-Ai -l!t:t - 4-5 -14 nj - fi-Sj - 7 -a II JO O -N ■30 JO 1 ; 1.-, ■.! \ 17 1 1 -17 1 J SO S -is-s! 1 Hi 1 1 11 'J 1 10 s i i:! 1 i ir. 10 17 l.'i 34 (H V.l \Vt. I 1.-, li -17 S -ir)S ■Jl 1 I -n \ --' 1 i -11 (I ] -I't H '' - s i\t\ ■J^ .11 SS OHBIT OF THK SPECTKOSCOPIC BINAHY A BOOTIS. 103 MKASIRKS OK A BOOTlH—fmliniied. mr2 7^s UJ,i-7.i4 U.T.' :);i() J20.' .'it4 lJ:iii()7L' i.'.")()i;it) I-'VJT'.-J IJSitTWl l:U4 Miti i:)i7 4.;ii 111)1 MKI 14iri J2S ii:i() .".(K) I Hi.' (HIJ l.'it'.l 7ti(l i')7i s\n V, \i Ciirv 7168 Vel. Wt -M 7| -2:i-7 ItudinI Vrlociv '22 li 21) S ;ii 5 ■J7 5 '-'S t) :ij U ■.'() 2 i-> li 2S :i 19 fi 17 1 71i)3 Vel Wt ■30 13 57 ■_'.; '.'S 31 3 ■■22H 30-3 7-22S Vel. ' Wt ■37.,Sj i ■2.V-,, J -291! J -35 71 J -3() ,S 2',M4 11 t)(j 23 2,S - U 31 ■2.V2 i ■2riit[ ! 3(ili i I 3I)-6| J ■38-9! J 33 37 (•27 23 (I 28 (3 15 Vel. ! Wt. -29t)! -32-4i -32-4: -37 21 -33 I -3r,.()j -3()t)l -43()| \'el. Wl -M 7 35-22 7 35 25 2.8 36 2 51-4 46-7 39 U 33-4 39 4 45-1 36 4 43 2 46 9 -4(1 9 7281 Vel. 1 Wt 43 in 42 52 5 67 25 28 l.s 72 -61-31 -65-51 } -51 o' i -43 2, -47-8J -42 1 -35-1 -32 -51 h -35 4 -46 3 5 -40 i -51 6 -40 9 -16-06 5 34 0-25 0-28 51 93 7288 \el. : Wt -43-9 -36-61 i -.5.3 9' i -43 o| -43 4| -44 7 -45 7 -45-7 -44-3| 44 58 3 (iO 25 28 48 71 I ••4 104 PlBhUATlONS OF THE DOMINION OBSEIU ATOUV. MEASrRES OF A BOOTIS— Tondiirffd. 4r.'7 4202 4'j;» 4-J7."i 4J'>J ■ 4JS'J 4;U4 4:n7 4:vj:> 41114 141'. 44:t() 4411J 4r)4',l 4r)7i 7 111 '.I'M) ■2(14 {)7'.' tillj SJit 131 -,).» 7(M) S(iti 4Jii ■ 79J ->(« 7iH) Sill Wcinhti-il \. i urv Rndial Volocitv 7.''.11 Vel. \Vt -47 5 J - "ili ■ 1 ' t -.-.1 J 1 -4:t - 4li ■ -4S- ^(il -47 ■•;; i 7:'. 17 Vil, Wt -■)5J> i -4S s i --ii:> ' -;(in I - 1(1 J 1 M .-. ^ -:iA.:i! -«■-! -4:i:t: VI ;!:t 4:1 ;s.'. 1 I'.' I) J'l (I'JS \V1. Wt VpI ; \Vi •19-6 -;!H-4 -:i!i',> -Hos; i ■J7 (I i -:i(i 11 5 t -;i-!ii 1 -4()',)| i ^ ;i4 4H - 4; :i7 -32 ;i -31) 4', -liVCi' -33.1! -20-4! i -39:)' -2S0 -IT) 4 Wl 1 ■J4 7 31-3 J9-5 28-3 24 .S 38-9 29 IIS 1 (Ml 2(i (I 2S 7340 Vi-1. Wt -3V 0: ; -43-7; i 1 -19.2J 5 -3(j o] 1 -30 1' i -2S-0| i -42-9 5 ^18.7! s -31 2 1 -23 Ci! 1 -27()i 1 -27:4 ; -33-31 1 73:>.' Vi'l Wt 3(1 10 2 7S 27 2s -22 4; i ■3-i9 Vil. Wt. - 3 Ij i ■h i 41 \ -13 -31-9 -2. ■ ( -24-8 -13-2 -31 -19-9 -2t 1 -3C. - 9-9 -28-11 1 - 21 37 + 4-91 - 27 - (I 2^ 17 (11 23 27 r. til 0-28 ■ 28 OKBIT OF THK SI'EL )StUPI(' BINARY A BOOTIS. 105 NORMAL PLACES. Hi: I'KKI.IMINAUV KI.KMKNTS r = Julian Day 2,420.r)r)2 0() A' = 18-() km. U) = 225° r = 0-50 7 = -2o*)4 km. /' = 211-90 davs M = l°-698r). .v.. .Jill si' il n 106 HI BLUAnONS UK TUi; UOMIMUN OBSEUVATUUY. OBSEUVATION EQrATION> ;l. 4. 5.. (). S. (1. 10 11 I'J -o:«is rdil'Jti -Id." -!-llSO -1 :iJ7 -OIW, -I :u-.' -11 11) - 1 14H -o<.>7;i -0 4(11 *i-jn5 +(I'J1() + 1 .'i.W +or)9s -oww +0 6;mi -0-9'.':i ^0 513 -0 070 TOi'.i:. -()-.">S7 -0 0.')4 + ()'.'IW -(»■ + 0- +0- + !)■ + 1' + 1 +0 + -0 -(I -1) (vl.') ;i:is 1 24 (141 'M)-2 ■m:> 18(1 (itil 17t 111 407 iiOi) -rO-4;iH -,0-70H ^0;i44 -0-,V,t.") -1 361 -10:50 -oos.-. -0 ls:i ^0 (tOJ ^0 i:i:t -0 lOJ rO JOO + 0- ^-■ +0- _ o -0 t1 -1 +-1 -0 -I) 0.") 44 01 OJ M \Vei(jhl. 10 13 07 7 0-7 1-3 17 1-3 13 10 1-3 1-0 wlicrc .r = 'h // = dK /' = Kd<- z = A'rfw n A'm ii -:^ 4:507 -2-5n!) = o -o-To:./. +1 miq f 1 •(i2()=o -f2!»72/) :ro.')iv --iti»s7-o + 7-427/* -7 ")f)77 -:? 90(i = n +<)1'.)Ck/ +r)()42 = n whence 'h- = +0 02 km dK = +0()2 km df = +0-04 doi = -I'-ns dT = -0 S2 (iii\ I UKBIT OF THE SPE( TKOSCOPIC; BINARY A BOOTIS. 107 When these eorrcctions were added to the approximate elements and the normal places rejjresented, Zpi- was lowered from 44 to 34. The individual observations were represented graphically and the residuals are Riven m th.- tables of the observations under the heading O-C. The Lick and Potsdam o})servations are very consistently jwsitive. Part of this dilTerence may be due to the scale of wave-lengths used, but some othei factor nmst be ojjerative also. The final elements are 7' = J. D. 2,420,561 IS ±0-90 A' = 18 02 km. + 0o9 w = 22.r-42 ±2°-60 <■ = 0-,54 ±0 024 7 = 2") -62 km. ±0 4.') P = 211-90 davs A- = r-Goso n sin ! = 44,000,000 km. '"'' '''"' ' t> M-r ., — 0/0 u The residuals from our own measures are often verv large, in one case thirteen kilometres. The agreement of the individual lines would lead one to e.Npect a probable error for a single plate between one-half and one kilometn., whereas it actually came out 2-8. The mea.sures were so discordant, that an investigation was undertaken to try and locate some reason for the erratic maimer in which the velocities behaved. Part of the trouble may lie in the star it.self, the conditions there clianging irregularly so as to alt.-r the api)arent wave-lengths of the lin<-s llie efT.'ct of such chang.'s are .small, provided they do not arise from a th.rd bo,iv. for the higher the dispersion employed and the more perfect th.- method of ob.servation the smaller do the variations in velocitv become Ih.s >s practically onclusiv,' evi.len.r, so f.,r as one-prism work is con- ••.■rned. that the anomali.'s in velociti.^s. f„r ^ood line stars at least, aris.- within the spectrograph. ••J iqovun-, trmpcraturc. cluin^c, ,K,ur focus, inrt^ulur i^uidi.ijl. nonun.lor.n iUun.inutun. of tl,r .■oUnnator, ra.h of these pluys i,s part .n the haul result Tl.e first thre,. .auses have bee., well n.et, and the modcru speotro- Krapl. is al.,.o>t ,.u ehanieally perfee, a..d free fro.n these detects \\.th good focus the daui^er fro... uouuniforn. ilUuiiinatio,. of the colh.uator vanishes. Tl... efTect of suidins; was fsted by taking; plates of A.-cturus, placing the stellar i...a^e first o,. one side of the slit and the., on the other. Ihe results of the.e experi...ents were published in the Astrono.n.cal ^oclety ot the Pa..iH<' Publicatiot.s, Aup.st, 191o. Thoy showed that veloc.t.es as „n.ch as thirtee,. kilo,..<.t,es f.-o... the truth, could he obtained by f^u.d.ng ,,,h the star ..ot perfectly c.tral o.. the slit. Wl.e,. one .-e.ne.nbers that ,he mnVnvA is do..e bv bh... fjree.. li«ht, while the plate registers the blue a,ul violet a..d that the i.nages of the star in these colours do not co.no.de. „,„, ,a„ .-eadilv s.^e that error co,.ld be int.-o.hiced in this way. There arc ,ther conside.-a,ions which lend pla..sibility to the suspicion that th.s source of ..rn.r i< verv ii.iportant. It would In- larger i.. o..e-prism than ui three- pri.,., instr,..,.e,.ts. It would be larger the sn.aller the telescope: for w:t. , ...Uill objc'tive the guiding image is fainter, th,- ,>ower .s lower and, ;.onse.,uentlv, it is ...ore dillicult to bisect the star with the sl.t of the spectroscope It would be larger in short-focus that, in long-foc.s telescopes, because the latter .vq.ii.v ...ore fre.,uent attentio.i in guiding and the imago i. shifted ofte.. from place to place, so that in the mean the whole sl.t .s better .■overed. Mo.eoN.r, the etTective in.age (the tren.ord.sk) is a er for long-focus i..stru...e,.ts, so that a slight displacement of the star probably alTects the ce.,t.-e of i.ite.iM.y ..f the in,age less than the same displacement i„ a telescope of shorter focus. These latter factors I believe to be vc,-y „„,,orta..t With the short-focus i..stn.me.,t used at this observatory ana ., ,,ock whi..l. ru..< very ..nifor...ly. a star will often stay in position tor ,if„,,,„ iHiimtes. This fact off., coupl..! with that of a temperature m the ,lo„,e n. winter as low as n.in..s 20 Fah.-e.,l.eit. wl.e.. to place the eye t.. ,he guidit.g tele..ope is to .-ec.ive the sensatio., of a., eh.ct.-ic shock, does not ,o„,ribu.e to constant attention to the position of the star image on the .li, (),H. might have a per.M.i.al eqiianon m bisecting the star image, so ,,,,„ a ..... of plates would all b.. co...siste..tly too high or t..o low. I art .„ „,.. .l„Te..,..Hr between the L.ck ( )bse,-vato.-y a..d Potsda... ami the Ottawa observatio,.s n.ight be accou,.te,l for i.. this way. Kxpe.-....ent to OUBIT OF THK SPECTUOSCOPU' BINAUV A BOOTIS. 109 asooriu.u the host niotluKl of Kuidins t<. socurc consistent rrsults would probably bo worth wlul... Tiu.s it might b,. found that slij-ht illumination "f the sht. so that It could b<> seen without the aid of the star's light would add to the a.ruraey. Personally, I find guiding .-asier in the twilight than on a dark night. In the case of A Hoolis, the n.ajoritv of the latter half of the i.lates were takei, und,T these con.iitions and in general thev give smaller residuals than the .'arly plates, but tlu' evidence is not sufficient to show whether this is to be ascribed to the twilight „• not 1 ••J Dominion Observatory. Ottawa, November. I'Jlo. liAlliAl. VhUKlTr ri-il\K ,i; A RodTI' ■ I It 51= n ••.' •••; **.' 1 3|' ! !S! \ 1 ,