Observer's guide
About NGC 581
NGC 581 (M103) is catalogued as an open cluster in Cassiopeia. Its J2000 position is RA 01:33:21.81, Dec +60:39:28.8, corresponding to 23.3392 degrees RA and 60.6589 degrees Dec. The local catalogue places it about 8,000 light-years away. Its referenced angular extent is approximately 7.4 by 7.4 arcminutes.
Observing tips
StarWatchr rates this as an easy target at magnitude 7.4. It is associated with autumn observing, with midnight placement typically strongest around October. From 52 degrees north its theoretical meridian altitude is about 81.3 degrees; local horizons and the live altitude chart determine the practical window.
A small telescope under reasonably dark skies is a good starting point; use the live altitude chart to choose its highest point.
What to expect
The SIMBAD classification for the matched source is OpC. A published radial velocity value is -45.3 km/s. The SIMBAD record currently connects it to 212 bibliographic references.
At roughly 7.4 arcminutes across, it benefits from a narrower field and adequate image scale. Use the listed 7.4 by 7.4 arcminute extent to check framing, and treat catalogue magnitude as integrated brightness rather than a direct measure of visual contrast.