Betelgeuse is intrinsically 60,000 times as bright as the sun NOW. The following is from MadSci.org (remember negative magnitudes are brighter when referring to stellar brightness):
The sun has a magnitude of -26, the full moon has a magnitude of -18 or
so. Sirius has a magnitude of -1.5 and is the brightest star in our sky.
Sirius is also one of the closest stars at 2.7 parsecs (about 8.5 light-
years). Betelgeuse is about 500 light-years away and has a magnitude of
about 1. Depending on how much of it's energy is in the visible spectrum,
it would probably be bright enough to rival a full moon. Somewhere in the
magnitude range of -18 to - 20. We would definitely notice it. It could be
visible during the day for several weeks possibly even a month or two. It
would be visible at night for several years.
It's my understanding that the full moon is essentially 7% of the brightness of the sun in a clear sky as viewed from the earth. The issue here is relative brightness to the average human spectator, not the intrinsic brightness of the stellar body.
But in any case, your Madsci.org suggests that a supernova'ed Betegeuse would be about the same brightness as the moon, not ten times greater. That seems more likely than 10x the brightness of the moon. That's all I was saying...