Planetary Nebula NGC 6804

NGC 6804
NGC 6804: Section of PanSTARRS DR1 color [147]

History

NGC 6804 was discovered on August 25, 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
NGC 6804: PN in Aquila; 500/2500mm-Newton + SBIG ST-6; Observatory Bülach; © 1996 Stefan Meister

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]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN 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)9° 13' 39"
Dimensions 35." (optical)
Distance 1.1 kpc
Radial Velocity-12.0 km/s ± 3.8 km/s
Expansion Velocity 24.0 km/s (O-III)
C-Star DesignationsAG82 373, CSI +09 -19291, HD 183932, PLX 4568
C-Star Magnitude14.47 mag (B filter), 14.37 mag (V filter)
C-Star Spectral TypeO9, O(H)
DiscovererPEASE 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 July to September.

Chart NGC 6804
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

NGC 6804
NGC 6804: Drawing; 200 mm SCT; © 7. 8. 1996 Stefan Meister

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.

— 1996, Stefan Meister

References

141Strasbourg-ESO Catalogue of Galactic Planetary Nebulae; A. Acker, F. Ochsenbein, B. Stenholm, R. Tylenda, J. Marcout, C. Schohn; European Southern Observatory; ISBN 3-923524-41-2 (1992); cdsarc.unistra.fr/viz-bin/cat/V/84 (2021-02-18)
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
465«Catalogue of 500 new nebulae, nebulous stars, planetary nebula:, and clusters of stars; with remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1802; DOI:10.1098/rstl.1802.0021
466«Observations of nebulæ and clusters of stars, made at Slough, with a twenty-feet reflector, between the years 1825 and 1833» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1833, Pages: 359-505; DOI:10.1098/rstl.1833.0021
467«Catalogue of nebulae and clusters of stars» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1864; DOI:10.1098/rstl.1864.0001