One evening, recently, I had 15 minutes to choose a target, set a sequence and get the whole shebang running. So I searched for any PNe close to zenith that looked interesting and got this - Abell 79. Another bonus - there are precious few pictures of it.

But it's really small, way to small for my focal length and so I could've used a bigger gun :-)

Anyway, two nights was all it took. Which feels quite weird after my usual months-long efforts to get one image done.

There was one surprise - there's a lot of Hydrogen everywhere in the frame. It's not quite faint enough to just ignore it and let it be but too faint to make it look interesting. So it's what it is - a kind of unresolved red ooze everywhere that I was forced to process. Unsatisfying result but I'm not going to spend tens of hours to image something that's just not right for my FOV.

The PN turned out quite well, fortunately, but showing it properly required a massive crop and no downsampling.

Full FOV Ha:

Ha closeup:

OIII closeup

Workflow:

1. H-alpha: DrizzleIntegration x2, DropShrink 0,9; OIII, RGB - normalna integracja;
2. BlurXterminator,
3. Ha Resample 50%, Catmull-Rom Cubic Spline Algorithm, Smoothness: 1,3
4. StarXterminator,
5. GradientCorrection
6. NoiseXterminator,
7. StatisticalStretch, Median: 0,1, no normalization.
8. Ha i OIII colorized in PS, Ha with dual-color Gradient Map, OIII with Hue/Saturation with the “Colorize” option checked.
9. TopazDenoise on darkest parts of Ha and OIII with masks - no “AI sharpening”.
10. Worked on colors, contrasts, details etc.
11. OIII screened on top of Ha.
12. Some final corrections, tweaks to color, contrast, saturation.
13. RGB stars, stretched with GHS and screened in PS.
14. Cropped, saved as png.

About the PN

Also known as PK102.9-2.3, PN G102.9-02.3, A79.

CDS Portal entry: http://cdsportal.u-strasbg.fr/?target=PN%20G102.9-02.3

DISCOVERY:
Discovered in 1947 by Rudolf Minkowski but not classified as a PN. Published again by George Abell in his 1955 PN catalogue and recognized as such.

BASIC ASTROMETRIC DATA:
Apparent size: 59 arcseconds.
Real size (assuming it's 14 566 light years from the Sun): 4,17 light year
Magnitude: 15,3
Distance: calculated from the parallax value published in GAIA DR3 - 4465 parsecs = 14 566 light years. However, some publications indicate it's much closer - ca. 5900 light years away.

CENTRAL STAR (CSPN):
"The Origin and Shaping of Planetary Nebulae: Putting the Binary Hypothesis to the Test" De Marco, DOI 10.1086/597765 describes the CSPN as an F0 V star. Such stars are main sequence stars of spectral type F and brightness class V. It's fusing hydrogen and has a surface temperature of about 6000-7600K. F0 V stars are about 1,5x the solar mass, with a diameter about 1,7x greater. They're also brighter than our Sun - about 7,2x brighter and emit yellow-white light.

Wait a second... this doesn't make sense. Main sequence Sun-like stars do not create PNe (yet).

According to "The binary fraction of planetary nebula central stars – I. A high-precision, I-band excess search" De Marco et al. MNRAS 428, 2118–2140 (2013) A 79 CSPN has surprisingly low temperature (for a central star of a PN, that is; true CSPNe can reach tens of thousands K). That means however, that this F0 V star is not the CSPN. It must be a binary star system, with the dwarf companion, which is the PN progenitor star to small and to close to the bigger star to be observable.

PN MORPHOLOGY:
This PN is of the bipolar type... kind of. Bipolar with benefits, lets say. According to "High-resolution spectroscopic observations of the peculiar planetary nebula Me1-1" Pereira et al. DOI: 10.1051/0004-6361:20078388 A 79 is similar in structure to Me 1-1. Such peculiar structure - consisting of a bright, central ring and fainter, not wholly developed lobes (hence- bipolar) strongly indicates that the CSPN is a binary. In fact, most of such PNe have a binary progenitor.