VdB 4 is an extremely faint reflection nebula illuminated by the star HD 217086. It sits inside a huge field of translucent interstellar dust in Cassiopeia, where most of the structure is only visible through scattered starlight. The bright blue core is the reflection component, while the pale “smoky” filaments around it are diffuse galactic cirrus—some of the lowest-surface-brightness structures in the northern sky.
This field is notoriously difficult to process because the nebula blends almost seamlessly into the surrounding dust. With enough integration time and careful calibration, the fine wisps, folds, and shadows begin to appear.
Imaging details:
🔭 PlaneWave CDK17
📷 ASI6200MM Pro
🎨 Astrodon LRGB filters
🕒 Total exposure: ~14.4 hours
🧮 Subframes:
• L: 569 × 60 s
• R: 34 × 120 s
• G: 60 × 129 s
• B: 50 × 120 s
📍 Roboscope Remote Observatory — Fregenal de la Sierra, Spain
by kbarth001