Planetary Nebula NGC 6804
![NGC 6804](/thumb/f9e446fb56dfab4b1cb58405a0771142_fig.webp)
History
NGC 6804 was discovered on 25 August 1791 by William Herschel using his 18.7 inch reflector of 20 feet focal length. He cataloged it as VI 38 and wrote: «considerably bright, small, irregular faint, easily resolvable. Some of the stars are visible.» Herschel misclassified it. His class VI stood for «very compressed and rich clusters of stars» [465]
His son John cataloged it as h 2043 in his catalogue of 1833, still considering as a cluster, but thought he saw some nebula. He wrote: «Sweep 88: Doubtful if a resolved cluster or a nebula of first class. Pretty large, round, brighter in the middle, 60"; with 2 or 3 accidental stars of the Milky Way. Sweep 89: A cluster. Has a 16m star, one or two 18m, and nebula. Sweep 196: A very small roundish cluster, 40" diameter, of very small stars, one brighter than the rest and = 15m. It is like a nebula well resolved, and is a curious object. Sweep 280: A very small compressed fan-shaped cluster of stars 11...18m, diam=1'; a 11m star on the north following side forms the vertex of the fan.» [466]
![NGC 6804](/users/sm/ngc6804_ccd_meister.jpg)
In John Herschels «General Catalogue» of 1864 he referred to that curious object as GC 4499 and noted: «cB, S, iR, rrr» (considerably bright, small, irregular round, well resolved). [467] That description as adopted by John L. E. Dreyer for his 1888 release of the «New General Catalogue». [313] It was only in 1917 that Pease recognized that this mysterious object was a planetary nebula.[141]
Physical Properties
Distance information to the sun can be found from 878 to 1726 pc. [145]
Designations | PN G045.7-04.5: NGC 6804, PK 45-04.1, ARO 34, VV 233, VV' 500 |
Right Ascension (J2000.0) | 19h 31m 36s |
Declination (J2000.0) | +09° 13' 38" |
Dimensions | 35." (optical) |
Distance | 1.1 kpc |
Radial Velocity | -12.0 ± 3.8 km/s |
Expansion Velocity | 24.0 (O-III) km/s |
C-Star Designations | AG82 373, CSI +09 -19291, HD 183932, PLX 4568 |
C-Star Magnitude | B: 14.47, V: 14.37 |
C-Star Spectral Type | O9, O(H) |
Discoverer | PEASE 1917 |
How to find NGC 6804?
The planetary nebula NGC 6804 is located in the constellation Aquila at about the same declination as Altair (α Aquilae). The 1° closeup from the DSS helps to identify the PN based on surrounding stars. Best observing time is from June to September.
![Finder Chart Planetary Nebula NGC 6804](/pic/charts/ngc6804_chart.webp)
Visual Observation
![NGC 6804](/users/sm/ngc6804_drawing_meister.jpg)
200 mm aperture: The object appears in the 8-incher with a relatively weak surface brightness. Although the shape was initially difficult to discern, the nebula appeared as an asymmetrical, bell-like structure. The central star is west of a brighter star, visible against the faint nebula. The brighter neighboring star lies approximately at the visual nebula limit.