On crisp autumn or early winter nights, as the constellation Andromeda strides across the sky, one of its quieter binary stars comes into view: Struve 79, also catalogued as STF 79. William Herschel first spotted this pair on September 16, 1782, recording it as H N 45 in his Catalogue of Double Stars, published four years later.
The two stars of Struve 79 are similar in brightness and relatively close together. According to Stelle Doppie, the primary shines at a magnitude of +6.04, while the secondary is slightly dimmer at +6.77. Separated by 7.8 arcseconds, they can be resolved with a telescope of 4 inches or larger under good viewing conditions.
Observers have often remarked on their subtle colors. The primary is a B-type star, hot and blue-white, while the secondary is an A-type star—hotter and more massive than our Sun—with a typical white hue. Bob Argyle noted a bluish tint in the pair, while Sissy Haas described them as “pearly white and pale blue-violet,” highlighting the delicate beauty of this stellar duo. For me, they look white, but with perhaps a slightly blue tint.
My Observations
| Date | October 30, 2023 |
| Time | 8:37 p.m. |
| Location | Seattle, WA |
| Magnification | 169x |
| Scope | Meade 8″ SCT |
| Eyepiece | 12mm |
| Seeing | Above Average |
| Transparency | Above Average |
While not the most spectacular binary, it’s a quietly lovely pair, showing subtle blue hints but mostly white as it glimmers against the autumn sky.
Key Stats
| Constellation | Andromeda |
| Best Viewing | Autumn |
| Visual Magnitude | +6.0 | +6.8 |
| Separation | 7.8″ |
| Position Angle | 86° |
| Distance | 388 light years |
| My Viewing Grade | B+ |
| Designations | SAO 36833, HIP 4675, STF 79, HR 282 and 283, HD 5789, 164 Andromedae, 164 And, Tycho 2811-02322-1 |
Sources and Notes
Webb Deep-Sky Society. (2019). Double Star of the Month Archive 2019. Retrieved September 14, 2025, from https://www.webbdeepsky.com/double-stars/2019/
Stelle Doppie. (n.d.). Struve 79 (STF 79). Retrieved September 14, 2025, from https://www.stelledoppie.it/index2.php?iddoppia=3938
MacEvoy, B. (2011). William Herschel’s Double Star Catalog. Handprint. Retrieved September 14, 2025, from https://www.handprint.com/ASTRO/Herschel_All.html
Sketch by Wayne McGraw
The Garden Astronomer 