Winnecke 4
M40 · Double star in Ursa Major
- Magnitude
- 9.1
- Size
- 0.8′
- Best months
- Mar, Apr, May
- Declination
- +58°
Messier's mistake: a faint double star logged while hunting a nebula that was never there. A single short sub shows all there is.
Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Imaging the double star
A double star needs one or two subs. There is nothing faint to accumulate.