The number 8 of the Messier Catalogue, more commonly named “Lagoon” is certainly belonging to the “Must have” of every astrophotographer. It is extremely bright and easily detectable with small telescopes. The nebula emits very strongly in Ha and OIII, thus in classical RGB photography the color is not red but purple. For astro-bginners, this is the typical low hanging fruit to start with. But for those located in France like me, this is not such a piece of cake as one would think. As a matter of fact, the nebula is at the meridian no more than 19 degrees over the horizon, thus the limitations are by far not only the limited time window to photograph it, but the very high risk to obtain a badly blurred image due to the strong turbulence. To obtain a qualitatively acceptable result of this beautiful and very colorful nebula, I therefore limited the photographic time frame only for 1h30 min prior and 1h30min after the meridian. As a matter of fact, my subs outside this window were of very low quality. Furthermore, it was key to select places with very low turbulence and I noticed that having an even small road in front of me was sufficient to generate turbulence due to the higher temperature of the asphalt. By selecting a grass ground, the turbulence was significantly decreased. Also, I only selected the most calm nights. Weather prediction programs such as the MeteoSuisse radar (which covers also part of France) helped a lot in identifying these regions.
About the rationale to shoot in HS-SHO, I noticed that the SII emissions are very particular on this nebula. As a matter of fact, although the SII emissions are significantly fainter than Ha and OIII, they reveal wonderful details invisible in RGB. I therefore decided to focus on the SII emissions, by adding a stronger contribution compared to Ha and OIII and to add it also in the Luminance channel with a 10% contribution (this is why the image is named HS-HSO).
From the color selection perspective, I pushed the balance to maintain part of the red-pink color of the nebula at the border, while highlighting the powerful OIII emissions and the increbible detailed structures of SII. Finally, the color selection is from my perspective more personal taste than anything else.
Of note, the nebula is incredibly bright at the center, while quite dim on the corners. So, I applied classical masks in LrC and in Adobe PS to avoid blowing the details of the complex heart.
At last, I compared my final version (my number 16) with the images obtained by other users located on south regions, and quite happily observed that even with a nebula so low on the horizon, it is still possible to capture details very close to those achieved with the nebula reaching close to the zenith.
Clear skies
Nicola