341 2278 342

O r i g i ~ d mir vorliegt, stimmen sehr gut untes einander. Um endlioh ganz siaher za seic, dass diebeidenVergleich- sterne keinen Fehler von einer Secunde enthalten, habe ich sie mit dem Heliometer verglichen. Schliesst man die drei Rectasceneionen nicht aus, so werden sie doch ~ sel-ir klein wird. nicht vie1 besser dargesteflt, aber die i t brigen Beobach- tungen merklich schlechter.

wie es die Darstellung der Beobachtungen vermuthen

liiest. Denn der Planet ist nicht lange beoachtet , und sein Lauf ist fast grdlinig und so bescfiaffen, dass, wie man auch 3Beobachtungen wahlt, der aus ilinen berechnete H a n s en'sche ,,massgebende Winkel'& immer

Die Ephemeride fur die im October d J. stattfindende ~ vierte Opposition wird in den Berliner Circularen er-

Uebrigens ist die erhaltene Bahn nicht so sicher, ~ scheinen.

On the Colour of Revolring Ihuble-Stars. By W. Uoberck.

In the following investigations concerning the co- In the first table the number of true binary systems lours of binary stars I have made use of the M e n s u - in the Xensurae Xicrometricae is given for every diffe- r a e M i c ro m e t r i c a e exclusively, as I thought this 1 rent Colour of the principal star and of the compa- better and easier than to use the colour-estimations of nion. different observers, in which case I should have been ' obliged to apply constant corrections to their result9 in ~

order to reduce them to Struve's standard.

A

Goldea Yellow Yellowish Yelsh wh. White Very white Green. wh. Bluish wh.

__ -. -

B

I White 'Very wh. i I

I Reddish Golden 1 Yellox 1 Yelsh. \I-h.

.___

- I

1 ; - 1 , 3 - - / - / - / - I -

1 - 1 -

l - 1 - I - - I _ - -_ , - I - 1 DO - I -

17 I - - -

6 i "-

- I - - - - , - I - - ; - / _ I _ _ I -

Ashy Bluish 1 Blue !Purplish / Purple I I I ~- ...__ -

16+1(3 39+18 19+ 9 9l+ll2

6 f 9 o+ 1

17+ 6

9 2 4 7 8

This table shuws at a glance that there are two the main star of a binary system is never b l ~ ; but - kihds of revolving double-stars. The first of which is composed of bodies, whose colours are s t r i c t 1 y i d e n- t i c a l , whereas the other embraces bodies, whose co- lours are generally c o rn p 1 e rn e n t a r y. - 'Phe prinoi- pal star in % d h cases is white or yellow, - wkihe &ars being mmt colnmon in systems of the 6rst kind. The cause of the apparent scaroity of ,,yellowish white" s h r s can only be attpibuted t o their -being called ,,yellvwish' and 8tmve remarks %hat ,,ashy." is very like ,,bllzish" and ,,prp1eu like ,,blue&. - It is therefore trae, that

" *

the companion is often blue, and the following five tables in which the stars are distributed according to distade, show that the number Qf bllne companions increases Ta-

pidly with the distance, while the components of very olose pairs are of shictly tihe same colow, It agrees well herewith that, as S t rwe has shown, the brightimss is on the whale more different, the more diffemnt the eolour i s , because it is known that the difference of brightness increases with the distance. -

34 3 2278 344

- - - - ‘ - 1 : Golden - 2 -

- - 6 - - - - - 7 - - * - I -

Yellow Yellowish - Yelsh. wh. - - - - 4 - - - - - - - - 15 - - White

Green, wh. - Very wh. - - - - - -- 2 -

_- / - - - 1 - - I I

1. D i s t a n c c < 0”X.

I ‘ _ I - - - 1 - 1 - - I - $ - I - -

h - / - - - 1 - 1 - l -

I l -

I ~

-

- I - 1 - 1 - i

I _ / - I _ _ I

Purple

Golden Yellow Yellowish Yelsh. wh. White Very wh. Green. wh.

- I - - 3 2 -

1 17

- 1 1

30

l -

1 -

l - I - I

-

.-

3. D i s t a n c e l”5-3”5.

Golden Yellow Yellowish Y elsh. wh. White Very wh. Green. wh. Bluish wh.

1 1 -

- 3 2 2 2 2 1

--

1 7 1 - 1 1 6 3 2

I 2 - ! -

1 I -

-

- 1

4. D i s t a 11. c e 3”5 - 6”5.

Golden Yellow yellowish Yelsh. wh. White Very wh. Green. wh.

- 2

- . 1

2 2 1

-

1 1 1

1

2

-

-

- - 3 1

2

5. D i s t a n c e > 6 ’ 5 .

Golden Yellow Yellovish Yelsh. wh. White Very wh. Green. wh.

1

1 -

1

1 I 1

1

-

-

- 1 1

345 22 78 346

- - - - -

1 - -

The number of greenish companions seems to in- crease with the distance, though those systems must be numbered among the first kind of double-stars. The relative frequency of binary stars of diff'erent distance i s somewhat different from that in a previous communi- cation, because so many close pairs have been discoverefi after the publication of the Mensurae Micrometricae. - The relative frequency of the two kinds of double-stars

3 11 13 27 41 84 76 12

is by the different distances respectively : 18.0, 7.3, 1.8, I . 1 and 0.5. - The distribution of the stars of the first kind has been referred to in a previous paper, - as for the blue binaries, more than one fourth of them lie in the galaxy, but they are else scattered ap- parently without order over the whole sky.

The following table exhibits the number of princi- pal stars of different magnitude and colour.

Bluish wh. I Golden Yelsh. 1 Yelsh. wh. -

- -

4 1 2 1 3 q 11 1 20

1 1 'x I 1

White 1 Very wh. h e n . wh. Yellow

1 1 6 8

10 3 4 2

1 3 4

2 1

4

- -

1 1 1 1 4 - - -

- 1 1 3

17 38 36

7 ____-

8 1 35 I 57 j 28 1 103 1 23 1 I5 1 1 I 270 The next table exhibits the number of companions of different magnitude and colour. -

Bluish

_- -

1 5 4 8 4 2

1 White wh.

1 1 1

5 16 9 52

-

I

?urplishl Purple 1 _- - - -

1 2 41+15 1 83+33

44+ 13 - 1 4 - 5

Yelsh.

1 - -

3 9

14 8 -

3 4

6 7 8 9

10

3

The corresponding examination of double stars dis- covered at Pulkowa and elsewhere has not yet been carried out, as far as I am aware of, and this would therefore be an interesting work for one of the new re- fractors. A large aperture is an advantage both with regard to light and owing to the necessity of having the

components distinctly separated. An average magnifying power is to be preferred as the higher powers are liable to bring out any uncorrected colour too much.

Markree 1879, August 23, IV. Doberck.

Osservazione dell' eclisse pmziale di sole del 19 Luglio. I due contatti vennero osservati con un ingrandimento di 150 e con elioscopio verde giallastro.

P r i m o c o n t a t t o : U l t i m o c o n t a t t o : 18 Luglio 20h lm426 t. m. di Venezia 18 Luglio 21Wlm22S5 t. m. di Venezia.

3. 48.33.6 t. sid. di Venezia. 5. 8.26.6 t. sid. di Venezia. Condizioni atmosferiche buone.

Latitudine geografica: Longitudine da Greenwich :

Osservatorio della Scuola nautica di Venezia.

45026 10" 5 Nord. Oh49m22 812 Est.

Prof. E. Millosevich.