|Object name:||Constellation:||Coordinates:||Apparent size:||Visual brightness:|
(= PK 045-04.1)
|Aquila||19h32m / +09°14'||1.1'||12.0 mag|
The planetary nebula NGC 6804 ("Snowball Nebula", "Incredible Shrinking Nebula", PK 045-04.1) in the constellation Aquila. NGC 6804 is an example of a multiple-shell planetary nebula with an oval inner shell breaking through the rounder outer shell structure. NGC 6804 is roughly 3,600 light-years from Earth. NGC 6804 was discovered by German-born British astronomer Frederick William Herschel in 1791. A few faint stars close to the nebula probably led Herschel to misclassify NGC 6804 as an open cluster of Class VI (rich and compressed cluster). Only after it was scrutinized more closely through the 100-inch reflector at Mount Wilson Observatory by Francis Pease in 1917 was its true nature uncovered (sources: Wikipedia / Phil Harrington. The Cosmic Challenge. Cambridge University Press (2019)).
Twenty-two 3-minute exposures (66 minutes total exposure) at gain 100 taken on July 21 / 22, 2022, were added for this shot with the Astro Pixel Processor (APP) software and the final image processing was done in Photoshop. Darks, flats, bias and dark flats were used.
Equipment: Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 16" f/4.5 "Ninja" dobsonian telescope riding on a dual-axis Tom Osypowski equatorial platform, Lacerta MGEN autoguider, Lacerta off axis system.