Statue of Liberty Under the Southern Tadpoles: A New Zealand Astrophotography Debut

This marks a significant milestone in my astrophotography journey, being my first full-colour narrowband image captured all the way from New Zealand. Primarily a landscape photographer by hobby, the transition to astrophotography and the challenges of image processing in PixInsight, including integrating third-party tools, have been a fascinating learning curve.

A Dusty Celestial Target

My primary target for this expedition was NGC 3576, also known as the Statue of Liberty nebula, or the Torchbearer. Its position within a dense, dusty region of our Milky Way made it an ideal subject. My goal was to gather enough narrowband data to illuminate the surrounding molecular clouds, which I'd admired in many images on Astrobin. The discovery of GUM 37, affectionately nicknamed the Southern Tadpoles, during data integration was a delightful bonus.

Navigating the Southern Skies

Packing and deploying equipment in a foreign land presented its own set of challenges. Coming from a consistently hot and humid climate, the biting cold and snow of New Zealand were a stark contrast. Driving over black ice and the occasional need to dig myself out of snowdrifts added an adventurous, albeit tedious, element to the project. I had planned for approximately 6 hours of data for each narrowband filter per night. While the SII and OIII nights were clear, the Ha nights were plagued by continuous cloud cover, forcing me to discard a significant portion of that dataset – a crucial lesson to factor into future expeditions.

The Art of Integration

Integrating the data was relatively straightforward, especially with the advantage of Bortle 1 skies in the Mackenzie District, which provided exceptionally clean data. Initial attempts to remove backgrounds using GraXpert and SETIAstro's Automatic DBE resulted in undesirable artifacts or missing sky sections. Consequently, I opted for a workflow involving BlurXterminator followed by a SETIAstro Statistical Stretch (15% target median) and smoothing with NoiseXterminator on each narrowband image.

After combining the stretched images into an LRGB representation (HSHO combination), I utilized StarXterminator to remove the stars. The subsequent purple cast was neutralized using an Invert > SCNR (Green) > Invert process. For the nebula itself, NarrowbandNormalisation was applied to balance the colours. Alternating rounds of CosmicPhotons' Colormask_mod and CurvesTransformation were then used to gradually enhance the blues and oranges characteristic of the Hubble palette. A final application of Cosmicphotons' StarReduction was key to allowing the nebula and dust to take center stage. The final touches were then applied in Photoshop.

Balancing the visual output proved to be the most challenging aspect. The cores of the Statue of Liberty and Southern Tadpoles were already intensely bright, requiring careful masking during curve adjustments to preserve detail in the surrounding dust. Despite these efforts, some core saturation remains – a point I intend to revisit once my processing skills have further advanced.

Overall, I am thoroughly pleased with the end result. This image represents the maximum clarity I could achieve for the dust without introducing visual artifacts. I've developed a strong affinity for the Hubble palette and focused on enhancing and protecting the complementary blue and orange hues. The final composition evokes a powerful image of a priestess reaching out towards the moon over a turbulent sea.

Until next time, New Zealand!

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For a higher resolution version of this image, please visit my Astrobin page: