Pickering's Triangle

*Pickering's Triangle from Everett Quebral's AstroBin gallery* *View on AstroBin: [https://app.astrobin.com/i/zavxuw](https://app.astrobin.com/i/zavxuw)*

About Pickering's Triangle

Pickering's Triangle — also known as Fleming's Triangular Wisp — is a filamentary portion of the Veil Nebula (Cygnus Loop) supernova remnant in Cygnus. It lies between the Western Veil (NGC 6960) and the Eastern Veil (NGC 6992/5), rich in teal [O III] emission intertwined with delicate H-alpha filaments.

Learn more about Pickering's Triangle on Wikipedia: https://en.wikipedia.org/wiki/Veil_Nebula

What Creates the Appearance

We see shock fronts from the ancient supernova plowing into surrounding gas. Oxygen-III glows a teal/blue where fast shocks excite doubly ionized oxygen; hydrogen-alpha reveals red, threadlike filaments. The geometry and magnetic fields create the intricate lacework.

The Science Behind the Beauty

Pickering's Triangle is part of the Cygnus Loop, the expanding debris of a massive star that exploded thousands of years ago. As the blast wave sweeps through the interstellar medium, it compresses, heats, and ionizes gas, which then cools and radiates in characteristic emission lines.

Capturing the Target

Equipment and Setup

Telescope/Optics: Explore Scientific 127mm ED APO Triplet with 0.7× reducer; Orion ED80T CF APO Triplet (earlier sessions)
Imaging Camera: ZWO ASI1600MM-Cooled
Filters: Astronomik Hα 12 nm, Astronomik O III 12 nm
Mount: Orion Atlas EQ-G
Guiding: Autoguiding with ZWO ASI120MM-S

Imaging Strategy

For this field, a bicolor HOO approach (Hα and [O III]) works well. Collect many long sub-exposures and balance total integration across channels to manage SNR. Typical total integration from this dataset: 20h 48m. Image resolution: 1824×1569.

Processing Techniques

Calibration: Apply darks, flats, and biases
Registration & Integration: Align and stack frames
Channel Combination: Map SII/Ha/OIII into palettes (e.g., Hubble palette)
Color Calibration: Balance narrowband colors while preserving structure
Stretching: Gradual histogram stretches to reveal faint structure
Detail Work: Noise reduction, deconvolution, and local contrast

The Surrounding Region

This target often sits within a rich region of gas, dust, and star-forming activity. Wide fields can capture multiple catalog objects, dark nebulae, and star clusters in the same frame.

Challenges and Rewards

Faint Structure: Demands long total integration time
Light Pollution: Narrowband can help under bright skies
Weather & Seeing: Stable conditions improve small-scale detail

Tips for Success

Plan sessions across multiple nights to build SNR
Balance narrowband channels and manage star sizes across filters
Use masks to protect stars and highlight nebular structure
Keep a non-destructive workflow for iterative refinement

Conclusion

A delicate web of shock fronts and emission lines makes Pickering's Triangle a rewarding narrowband target, revealing exquisite structure with sufficient integration and careful processing.

Technical Data

Object: Pickering's Triangle
Constellation: Cygnus
Integration: 20h 48m
Resolution: 1824×1569 px
Filters used: Hα, O III

Equipment

Imaging Equipment

Optics: Explore Scientific 127mm ED APO Triplet + 0.7× Reducer; Orion ED80T CF APO Triplet
Camera: ZWO ASI1600MM-Cooled
Mount: Orion Atlas EQ-G
Filters: Astronomik Hα 12 nm, Astronomik O III 12 nm
Accessories: EQ Focuser
Software: PixInsight 1.8 Ripley

Guiding Equipment

Guide Camera: ZWO ASI120MM-S
Mount: Orion Atlas EQ-G
Accessories: EQ Focuser