Abell 39 (Hercules)
Fig. 1 - Eerily glowing bluish bubble: The remarkably symmetrical planetary nebula Abell 39 in Hercules, photographed with a 16-inch f/4.5 Dob on an equatorial platform.
| Object name: | Constellation: | Coordinates: | Apparent size: | Visual brightness: |
|---|---|---|---|---|
| Abell 39 (= PK 047+42.1) | Hercules | 16h28m / +27°55' | 2.6' x 2.6' | 15.5 mag |
The low surface brightness planetary nebula Abell 39 (PK 047+42.1) in the constellation of Hercules. Abell 39 is a big cloud of gas expelled from an unstable dying star and was identified by George O. Abell from Palomar Survey plates in 1955. It is 3,800 light-years from earth, about 1.4 light-years across and has expanded for 11,000 years (Sources: Wikipedia).
Exposure time: 2h 3min (41x approx. 3min) at ISO 800, taken on June 21 / 22, 2014, the shortest night of the year. Processing with Deep Sky Stacker and Photoshop. No calibration frames were taken. Note: The dark background surrounding the nebula consists of only 20 exposures (not all 41 exposures could be used due to a different framing of the images). For the nebula itself, all 41 exposures were used.
Equipment: Canon EOS 450D Baader modified camera, TeleVue Universal Paracorr 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.
Field of view comparison: image of the moon with the same setup.
Fig. 2 - Star hopping to Abell 39: A nice starting point is the constellation Corona Borealis. First find the stars Iota and Epsilon Coronae Borealis. Search chart 1 for Abell 39. Copyright 2025 'The Mag-7 Star Atlas Project', www.siaris.net.
Fig. 3 - Star hopping to Abell 39 from an area close to Iota & Epsilon Coronae Borealis. The circles correspond to a 1.5° field of view (e. g. a 40 mm 65° eyepiece on a 16" f/4.5 telescope). Search chart 2 for Abell 39. Copyright 2025 'The Triatlas Project', https://www.uv.es/jrtorres/triatlas.html.