Repeated imaging observations have been made of NGC 3982 with the Hubble Space Telescope between March and May 2000 , over an interval of 53 days .
Images were obtained on 12 epochs in the F 555 W band and on five epochs in the F 814 W band .
The galaxy hosted the type Ia supernova SN1998aq .

A total of 26 Cepheid candidates were identified , with periods ranging from 10 to 45 days , using photometry with the DoPHOT program .
The de-reddened distance to NGC 3982 is estimated from these data using various criteria to maximize signal to noise and reliability : the values lie between 31.71 and 31.82 , with uncertainties in the mean of typically \pm 0.14 mag for each case .
A parallel analysis using photometry with HSTphot discovered 13 variables , yielding a distance modulus of 31.85 \pm 0.16 .
The final adopted modulus is ( M - m ) _ { 0 } = 31.72 \pm 0.14 ( 22 \pm 1.5 Mpc ) .

Photometry of 1998aq that is available in the literature is used in combination with the derived distance to NGC 3982 to obtain the peak absolute magnitude of this supernova .
The lower limit ( no extinction within the host galaxy ) for M _ { V } is -19.47 \pm 0.15 mag .
Corrections for decline rate and intrinsic color to carry these to the reduced system of Parodi et al .
( 2000 ) have been performed .
The derived luminosities at hand are fully consistent with the mean of the 8 normal SNe Ia previously calibrated with Cepheids .
Together they yield H _ { 0 } \approx 60 \pm 2 ( internal ) { km } { s } ^ { -1 } { Mpc } ^ { -1 } based on an assumed LMC distance modulus of 18.50 .
We point out that correcting some of the systematic errors and including uncertainty estimates due to them leads to H _ { 0 } = 58.7 \pm 6.3 ( internal ) { km } { s } ^ { -1 } { Mpc } ^ { -1 } .