Our results therefore indicate that the central portion of this nebula is in rapid rotation, in the sense that a point on the major axis of figure some 18 southeast of the center is receding from us, relatively to the corresponding point northwest of the center, with a velocity of 14.9 km. per second.

This is the "Omega" nebula.33 The slit was directed upon the brightest region. The Hẞ line is intermediate in brightness between N, and N2.

A little longer exposure time would have increased the accuracy.

N.G.C. 6620. a 18h 15m6; d=-26° 53′; λ=273° 29′; ẞ——3° 29'

This nebula is just distinguishable from a star (4" to 5" diameter) and its image appears perfectly round. All of the spectrograms were taken with the slit along the east and west diameter of the nebula. The lines are not good on any of the plates, due to under-exposure. They do not show any certain evidence of inclination.

33 See Publ. Lick Obs., 8, pl. 58, 1908.

N.G.C. 6629.

= +0° 7'

= 18h 19m6; 8 -23° 15′; λ=274° 30′; ß:
The lines recorded have relative intensities approximately N, N2 HB :: 10:32.

Remarks

2

N1 N2 HB

Miss Hobe

+161 1

Lines in good strength

N, N2 HØ

+14

90°

The hydrogen radiation is relatively faint in this object.

The nebula is "stellar" and the lines on the last two plates are short and stubby. On neither spectrogram is there any evidence of inclination of the nebular lines, but this may be a consequence of inadequate accuracy in guiding upon so small an object.

=

N.G.C.2 4732. 18h 279; α= 8 -22° 43′; λ=276° 26′; B +0° 35' This "stellar" nebula is of very small diameter. The hydrogen radiations are relatively faint. The ratios of intensities on the spectrograms are estimated as N, N2 : Hß :: 10:3 : 1. The N1 and N2 lines on the last plate show no evidence of inclination, possibly because of the small diameter of the nebular image.

1

2

The first six observations were made at Mount Hamilton and the last three at Santiago, Chile. The hydrogen radiations seem a little stronger than normal; N, : N2 : Hß :: 10 : 3 : 11⁄2.

Remarks

142.2 144.3 -151.0 -142.2 -142.8 -146.0

-143.2 1

long

Hẞ v. ft. N, over-exposed

90°

-146.6 1

long 90°

Hẞ v. ft.

-144.4 2 V-145.4

long

90°

-33° 27′; λ

=

All lines fully exposed

90°

+15.6 1

90°

1-pr. 16-in.

long

long

Poor conditions

Poor plat

long

Fine plate

+16.2

90°

Moore

N1 N2 HB

+18.4

10: 3:1

long Hẞ ft.

2 204°

The agreement of the Mount Hamilton and Santiago results is satisfactory.

This nebula is just distinguishable from a star. It has a small wing in position angle 24°. The three plates taken with slit in the two positions furnish no certain evidence of inclination of the lines. The guiding in the Mount Hamilton observations, owing to the far-south position of the nebula, was not perfect.