We present HST photometry of the resolved stellar population in the dwarf irregular galaxy NGC 1705 .
The galaxy has been observed with both WFPC2 and NICMOS , and successful images have been obtained in the F555W , F814W , F110W and F160W bands .
The optical fields cover most of the galaxy , while the infrared field ( NIC2 ) maps only its central regions .

The optical photometry provides \sim 20000 objects down to m _ { F 555 W } \lower 2.58 pt \hbox { $ \sim$ } \kern - 7.75 pt \raise 2.795 pt \hbox { $ < $ } 29 in the PC field of view and \sim 20000 in the three WFCs .
In the infrared we have been able to resolve \sim 2400 stars down to m _ { F 110 W } , m _ { F 160 W } \approx 26 .
A subsample of 1834 stars have been unambiguously measured in all the four bands .
The corresponding color-magnitude diagrams ( CMDs ) confirm the existence of an age gradient , showing that NGC 1705 hosts both young ( a few Myr old ) and very old ( up to 15 Gyr old ) stars , with the former strongly concentrated toward the galactic center and the latter present everywhere , but much more easily visible in the external regions .

The tip of the red giant branch ( TRGB ) is clearly visible both in the optical and in the infrared CMDs and allows us to derive the galaxy distance .
Taking into account the uncertainties related to both the photometry and the TRGB magnitude – distance relation , we find that the distance modulus of NGC 1705 is ( m - M ) _ { 0 } = 28.54 \pm 0.26 , corresponding to a distance D = 5.1 \pm 0.6 Mpc .