Observer's guide
About NGC 3556
NGC 3556 (M108) is catalogued as a spiral galaxy in Ursa Major. Its J2000 position is RA 11:11:30.97, Dec +55:40:26.8, corresponding to 167.879 degrees RA and 55.6741 degrees Dec. The local catalogue places it about 45,000,000 light-years away. Its referenced angular extent is approximately 14.59 by 3.87 arcminutes.
Observing tips
StarWatchr rates this as a hard target at magnitude 10. It is associated with spring observing, with midnight placement typically strongest around March. From 52 degrees north its theoretical meridian altitude is about 86.3 degrees; local horizons and the live altitude chart determine the practical window.
Because it is faint, use a larger aperture where possible, avoid bright Moon conditions, and use averted vision.
What to expect
The SIMBAD classification for the matched source is AGN. SIMBAD records the morphology as SA. A published radial velocity value is 699 km/s. The SIMBAD record currently connects it to 501 bibliographic references.
At roughly 14.6 arcminutes across, it benefits from a narrower field and adequate image scale. Use the listed 14.59 by 3.87 arcminute extent to check framing, and treat catalogue magnitude as integrated brightness rather than a direct measure of visual contrast.