How bright will the supernova initially appear momentarily during the 'breakout' spike, compared to the Moon?

Answer

As brightly as a thin crescent Moon

The initial shockwave breaking through the outer layers causes a temporary luminosity boost by a factor of about 7,000, making the star momentarily shine as brightly as a thin crescent Moon.

How bright will the supernova initially appear momentarily during the 'breakout' spike, compared to the Moon?
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