Every blackbody color calculator I've managed to find only calculates hue and saturation; they completely ignore brightness, which severely limits their usefulness if you're trying to model the actual appearance of a hot object.
I've tried looking for how to calculate it myself, but Google is choked by discussions about color temperature for monitors; every discussion I come across is focused on particular applications besides finding the color for hot objects.
I understand the range of perception for the eye changes depending on ambient light. We're looking at hot objects in space, from 500 to ~7000 K, so let's assume it's equivalent to a moonlit night (lower end of mesopic vision).
I'm guessing what I need is some form of Planck's Law or the Stefan-Boltzmann Law, for visible light only. Then I need to figure out how to convert the power given by those laws into a luminance value for graphics software (ranges between 0% for a non-emitting object and 100% for a glowing white object). The sources are surfaces, not points.
I think I can use the SB Law, I'm just not sure how to get from there to the final brightness value.
Thanks for your help.