The Elephant Trunk Nebula: A Striking Celestial Formation Captured in HOO

Behold the majestic Elephant Trunk Nebula, also cataloged as IC1396! This breathtaking emission nebula, located in the constellation Cepheus, is a well-known object among deep-sky observers and astrophotographers. Its distinctive shape, reminiscent of an elephant's trunk, is sculpted by stellar winds and radiation from the bright star HD 207500, which is hidden within the dusty clouds.

This particular capture utilizes the HOO narrowband processing technique, which leverages the light emitted by doubly ionized oxygen (OIII) and singly ionized hydrogen (H-alpha). This method often brings out vibrant and striking colors, highlighting the intricate structures within the nebula.

Acquisition Details

The journey to capture this celestial marvel began on August 12, 2025, from a backyard observatory with a Bortle 5 sky. The data was meticulously acquired using NINA and PHD2 for guiding.

• Ha: 21 x 300" (1 hour 45 minutes)
• OIII: 21 x 300" (1 hour 45 minutes)
• R: 22 x 30" (11 minutes)
• G: 22 x 30" (11 minutes)
• B: 22 x 30" (11 minutes)

Camera settings were optimized for performance: Gain 200, offset 55, and a temperature of -5°C. A robust set of calibration frames, including 50 darks, 30 flats, and 30 dark flats, were used to ensure the highest quality data.

Equipment Used

The following equipment was instrumental in acquiring these stunning details:

• Telescope: GSO RC6
• Camera: ZWO ASI2600MM Pro
• Filters: Antlia V-Series LRGB and SHO 3nm Narrowband Filters (2” Mounted)
• Filter Wheel: ZWO Filter Wheel
• Autofocus: ZWO EAF
• Mount: iOptron GEM 28
• Off-Axis Guider: ZWO OAG-L with ASI174MM Mini

Processing Workflow

The raw data was transformed into this final image using a combination of DeepSkyStacker (DSS) and Adobe Photoshop.

1. Stacking: All individual sub-exposures were stacked using DSS to create a single, clean image.
2. Initial Stretch: A first stretch was applied in Photoshop to reveal the basic structures.
3. Star Removal: The StarXTerminator tool was used to isolate the nebula from the stars.
4. Detail Stretch: A second stretch was performed on the starless image to enhance target details.
5. Color and Contrast: Curves adjustments were made to improve contrast, followed by saturation and color adjustments.
6. Noise Reduction & Sharpening: NoiseXTerminator was employed for noise reduction, and the Smart Sharpen filter was used for sharpening.
7. Star Integration: Finally, the original RGB stars were added back to the image using a screen layer to complete the composition.

This meticulous process results in an image that not only showcases the intricate beauty of the Elephant Trunk Nebula but also highlights the power of narrowband imaging and careful post-processing.