269 241 7 170

B e m e r k u n g e n.

1881 Oct. 8.

3 15. 3 28.

Nov. 9.

(55) Pandora . Wolkenschleier. Stiirmisch.

(61) Danae . Sturm. Unruhige Bilder. Dunst. Planet schwach.

(37) Fides . Unruhige Bilder.

1881 Nov. 20. Sturrn. Der Tubus schwankt bisweilen, daher wurden die Aa unsicher.

(87) Sylvia. 3 26. Die kleine Registriruhr hat schlecht re-

gistrirt, daher wurden die Aa wegge- lassen.

Dresden 1881 December 5. B. v. Engeihardt.

Ueber eine Einrichtung zu bequemer Ablesung der Declination an einem Aequatoreal. Aus einem Schreiben des Herrn 3: M Schaeberle, Assistent der Sternwarte in Ann Arbor, an den Herausgeber.

Fitted to and concentric with the bearing of the de- clination axis is a beveled gear wheel A in which runs another beveled gear wheel a (exactly one fourth of the size of A) fitted to a metallic rod running in two bearings which are fastened to the telescope tube. One of the bea- rings being close to the wheel a, the other at the eye-end of the telescope tube; fastened to and concentric with the latter, is a flat circular disk whose circumference is divided into 90 parts, each of which representing one degree of declination. A vernier or pointer fastened to the metallic rod, after being once properly set, will always indicate either the declination or the complement of the declination of the point in space to which the telescope is directed. To se- cure a smooth and close working of the teeth in each other, the box or bearing near the wheel a should be allowed to have a slight motion in a line parallel to the declination axis ; a spring being placed underneath the box to keep the wheel a in contact with A, the pressure will be practically constant for all positions of the instrument.

Ann Arbor, Michigan, I 88 I Nov. 30.

Projecting rims (which roll upon each other) forming nearly a continuation of the cones containing the surfaces of the teeth on a and A, are there turned off SO that the teeth shall work in each other to the proper depth.

For an instrument already mounted the wheel A can be cast in halves, which in finishing are bolted together; with the aid of set-screws it can be fastened to, and cen- tered in its proper place. The circular disk can be gra- duated with the aid of the declination circle by setting the telescope to every whole degree of declination and marking the positions of the pointer. To eliminate any slight errors due to eccentricity in the wheels A and a, four concentric circles should be described on the disk and graduated as above, each circle belonging to its proper quadrant. By causing the last motion of the telescope to be such that the readings of the circle either always increase or decrease, the error in the setting due to the play between the teeth will be eliminated. The graduated side of the disk should of cour6e face the observer.

J. M: Sckaeberle-

Schreiben von Prof. R. Wolf, Director der Sternwarte in Zurich, an den Herausgeber.

Ich sende Ihnen die Nr. 54 meiner Mittheilungen und die gewohnte Anzeige derselben fur die Astronomischen Nachrichten, welche diesmal ganz kurz ausfallen kann.

Die soeben im Drucke vollendete Nr. 54 meiner Astronomischen Mittheilungen enthalt meine zweite Mit- theilung iiber eine neue Reihe von Wiirfelversuchen, welche, da sie hauptsachlich den Rest der Versuche selbst giebt, und nur einige Resultate andeutet, welche in einer dritten Mittheilung gegeben und discutirt werden sollen, keinen Auszug gestattet. Nachher folgt eine zweite Serie der von meinem Assistenten, Herrn A. Wolfer erhaltenen und berech-

neten Sonnenfleckenpositionen, welche das zweite Halbjahr I 880 beschlagt , und natiirlich ebenfalls keinen Auszug gestattet. Den Schluss bilden die Nummern 445-450 der Sonnenflecken - Literatur , in Beziehung auf welche bemerkt werden mag, dass Nr. 449 eine chronologische, Nr. 450 aber eine alphabetische Uebersicht uber die bisherigen Nummern, und damit eine langst gewiinschte Erleichterung fur deren Benutzung bsingt.

Ziirich 1882 Jan. 27. R. Wolf .