Abell 74 in Vulpecula

Abell 74 in Vulpecula

Ancient Planetary Nebula

Constellation: Vulpecula
Ra: 21h 16m 52s
Dec: +24d 08m 05s
Distance: 2,500 light years
Image Size: 15' x 13.5'
North: Lower right



Abell 74 is a large, ancient planetary nebula in Vulpecula at RA 21h 16m 52s and DEC +24d 08m 05s. It is also designated at PK 72.7-17.1. The object is mostly circular with an apparent diameter of 13.5′ although it appears to have additional structure extending N-S to perhaps 15′. North is to the lower right. It has a white dwarf central star (WD 2114+239) with an effective temperature of 108,000 K. Distance measurements for planetary nebula have a wide variance. The distance provided for Abell 74 is ~ 2,500 light years. It is very faint, and much stronger in H-a than OIII. It is classified by Tweedy and Kwitter (1996ApJS,107..255T) as a Type F that appears to be uniformly filled, and with an OIII zone present that is considerably smaller than the H-a. Abell 74 is interacting with the interstellar medium (ISM).

My image contains a total 14.5 hours of exposures taken over several nights. The high contrast from very narrow (3 nm) H-alpha and OIII filters was utilized to bring out structure in this faint PN. H-a was mapped to red/magenta and OIII was mapped to blue-green (teal) to represent the color we would see if this object were bright enough to activate the cone sensors in our eyes. 1 hour of RGB data were included for star colors using a G2V (sunlike star) white point balance.

Exposure: 14.5 hrs Total: 6 hrs H-a, 7.5 hrs OIII, 1 hr RGB
Telescope: RCOS 16
Mount: Software Bisque Paramount ME
Oag: Astrodon MonsterMOAG
Acquisition: CCD AutoPilot4
Calibration: CCDStack2
Observatory Site: Sierra-Remote Observatories, Shaver Lake, CA
Camera: Apogee U16M
Filters: Astrodon 3nm OIII, H-a, Gen 2 RGB
Guider: SBIG ST-402
Camera Operation: MaximDL4.62
Processing: Photoshop CS5 Extended
Image Date: 06/28/2011 - 07/02/2011

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