GC 5585 is a faint spiral galaxy located in the northern constellation Ursa Major, about 28 million light-years away from Earth. It lies within a rich area of the sky, near the more prominent M101 galaxy (the Pinwheel Galaxy), but NGC 5585 is much smaller and dimmer, making it a more challenging target.
This galaxy was discovered by British astronomer William Herschel on April 17, 1789. Herschel is best known for discovering the planet Uranus and cataloging thousands of deep-sky objects using large telescopes he built himself.
NGC 5585 is classified as an Scd-type spiral galaxy. That means it has loose, patchy spiral arms and a relatively small central bulge. What makes this galaxy particularly interesting to astronomers is its high amount of dark matter. While its visible matter — stars, gas, and dust — appears spread out and relatively dim, the galaxy’s rotation speed suggests it has far more mass than what we can see. Most of that hidden mass is thought to be dark matter.
Published: Jun 7, 2025
Total integration: 3h 42m
Integration per filter:
- LP: 3h 42m (111 × 120″)
Equipment:
- Telescope: Celestron NexStar 8SE
- Camera: ZWO ASI294MC Pro
- Mount: Juwei 17
- Filter: Optolong L-Pro 1.25″
- Software: Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging ‘N’ Astronomy (N.I.N.A. / NINA)
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