NGC 6884 (PK 82+7.1) Planetary Nebula in Cygnus

Located at: RA 20 hours 10 minutes 24 seconds, Dec +46 degrees 17 minutes 38 seconds

Size: 6.0" Magnitude: 12.6 photographic Class: 2b

North is up

West to the right

Telescope:

 14.5" f5 Newtonian reflector

Camera:

 ST-8XME, self-guided, binned 1x1, temp -20c, camera control MaxIm DL 4.56

Image:

 Lumicon Red filter, 70 minutes (70 x 1 minute {60 seconds} subs), 07/6/2015; seeing 2.2-3.1 FWHM per CCDStack

Processing:

CCDStack 2.90.5589.16047, Photoshop CS5.1

Location:

 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)

Notes:

I tried to image some high surface brightness planetaries on a rare clear night during monsoon clouds. This, and PK 64+5.1, were imaged the same evening while rising in the east ..

View 200% crop.

Contemporary Visual Observation(s) for NGC 6884
NGC 6884 = PK 82+7.1 = PN G082.1+07.0 = N6766
20 10 23.6 +46 27 40
V = 11.0;  Size 6"x5"

17.5": bright, very small, very high surface brightness.  Appears as a slightly 
out of focus mag 11 bluish star at 100x.  Moderate contrast gain using an OIII 
filter.  At 412x appears prominent with a very small 5" blue disk.

13": fairly bright, very small, high surface brightness, definite bluish disk at 
166x, excellent contrast gain with OIII filter.  Easily takes 350x due to 
surface brightness.

- by Steve Gottlieb
Historical Research Notes / Correction for NGC 6884
NGC 6766 = NGC 6884.  Things were not looking good for this stellar planetary 
discovered by Pickering -- until Dave Riddle began digging around in the old 
literature.  There he found a paper by the Reverend Thomas Espin (MNRAS 72, 
150, 1911) in which Espin quotes Pickering as correcting the published 
position by one hour of time (20h instead of the original 19h copied into 
NGC).  The corrected position is also the one which Pickering published in HA 
60, where N6766 is tellingly out of numerical order, though without the 
additional NGC number (from Copeland whose position is good).

Pickering's early method of finding the planetaries is interesting:  he simply 
swept the sky looking through a low-dispersion spectrograph attached to his
telescope.  The stars' spectra would have appeared mostly continuous through 
his instrument, while the planetaries would still appear as stellar points 
because most of their visible light is concentrated in the emission lines of 
oxygen at 4958 and 5007 angstroms.  Pickering later pioneered the use of 
objective prism photography, and several planetaries were found on Harvard 
plates as a result, primarily by Wilhelmina Fleming. 
 - Dr. Harold G. Corwin, Jr.