The constellation Draco winds across the northern sky like a celestial serpent, home to both well-known stars and hidden gems. Among these treasures lies the binary star Struve 2155 (STF 2155). Though it’s not the brightest or most famous star in Draco, this pairing rewards patient observers with a delicate split and an attractive contrast in brightness and color.
Next to the soft glow of a 7th-magnitude yellow star sits a delicate blue companion of 10th magnitude, located just 10 arcseconds away. The primary yellow star is classified as a yellow-white giant star, which is bigger, hotter, and brighter than the Sun. The pair lies nearly 600 light-years away. Stephen James O’Meara captures it well in his article for Astronomy magazine, describing this pair as a dimmer cousin of Albireo.
With a telescope boasting an aperture of 4 inches (100 mm) or more, you can confidently observe this nice pair. When using larger apertures (6–8 inches / 150–200 mm), you’ll truly appreciate the vibrant colors and clearly see the separation.
While Albireo in Cygnus may always be renowned for its striking color contrasts, double stars like Struve 2155 remind us that beauty in the night sky often lies in subtle details. I’m sure Friedrich Georg Wilhelm Struve felt this way when he first logged this pair around 1830. This quiet yellow-and-blue duo offers a small but satisfying prize—a reminder that the dragon of the north has treasures hidden in its scales.
My Observations
| Date | June 1, 2021 |
| Time | 10:45 p.m. |
| Location | Seattle, WA |
| Magnification | 145x |
| Scope | Meade 8″ SCT |
| Eyepiece | 14mm |
| Seeing | Average |
| Transparency | Average |
On this late June night, I find my way through the constellation Draco. Struve 2155 stands out as a small but striking binary star system among its stellar neighbors. The primary star emits a warm yellow glow, while its companion shines in a beautiful blue. The contrast between these two dimmer stars is captivating.
Around them, several other stars frame the pair, adding subtle depth to the view. In this peaceful moment, with only the soft hum of the night as background, the colors and companionship of Struve 2155 remind me of how extraordinary even the smallest points of light in the sky can be.
Key Stats
| Constellation | Draco |
| Best Viewing | Summer |
| Visual Magnitude | +6.9 | +9.9 |
| Distance from Earth | 595 ly |
| Separation | 9.96″ |
| Position Angle | 112.7° |
| Milky Way Location | Orion Spur |
| My Viewing Grade | B+ |
| Designations | SAO 17410, HIP 84465, HD 156890, 4198-01479-1, BD+60 1742 |
Sources and Notes
Stelledoppie. (n.d.). Struve 2155. Retrieved August 16, 2025, from https://www.stelledoppie.it/index2.php?iddoppia=69203
Sketch by Wayne McGraw
The Garden Astronomer 