The light curve of the Type Ia supernova SN1974G ( in NGC4414 ) is important because the Hubble Space Telescope has measured the distance to the host galaxy by means of Cepheid variables and thus the Hubble Constant can be derived .
Light curves from the secondary literature are inadequate since the majority of data is misreported , the majority of the published data is overlooked , and the majority of all data is unpublished , while comparison star sequences have offsets of over half a magnitude .
I have recovered and validated all data , remeasured the comparison stars , and performed light curve template fits .
I find the observed peak B and V magnitudes to be 12.48 \pm 0.05 and 12.30 \pm 0.05 , with a decline rate of \Delta m _ { 15 } = 1.11 \pm 0.06 .
For E ( B - V ) = 0.16 \pm 0.07 , the unabsorbed peak magnitudes are B = 11.82 \pm 0.29 and V = 11.80 \pm 0.22 .
With the distance modulus to NGC4414 as \mu = 31.41 \pm 0.23 , I find H _ { 0 } = 55 \pm 8 km \cdot s ^ { -1 } \cdot Mpc ^ { -1 } .