Can anyone enlighten me on how to convert Joules to glowing needle degrees?
Here is the equation you need:
Q = mC(T2-T1)
note: (T2-T1) is generally written as deltaT
Q = Heat energy(Joules)
m = mass(grams or Kg depending on which val used for 'C')
C = specific heat capacity(Joules/(gram*degreeCelsius) or Kg...
So you want to find 'Q'. You need to know the 'C' of your needle. I would just look for specific heat of steel. And you need to know its mass. As for the change in temp... I don't know what temperature makes things glow so you will have to guess. I think its completely possible, but figuring out how to discharge the capacitor(s) in an effective way might be challenging. Be sure to post some pictures of this when all said and done.