THE DISTANCE SCALE
Distance measurements are one of the most complex task performed in Astronomy.
They affect almost all fileds of astrophysics, perhaps most importantly,
our knowledge of the value of the Hubble constant.

Observations of nearby galaxies are used to calibrate the distance scale
of the universe, and to investigate systematic errors of our measurements.

Recent results will let us achieve 1% accuracy of the distance measurements
in the near future.
2013, Natur, 495, 76
TRGB
Over the past decade, the Tip of the Red Giant Branch (TRGB) method
has been successfully applied to most of the nearby galaxies,
resulting with an independant estimation of the Hubble constant.

However, the very strong influence of the reddening and population effects
affecting the brightness of the TRGB limit the accuracy of this technique.

To take a full advantage of this method of distance measurements it is crucial
to employ the calibration of the TRGB that minimizes errors arising from
the reddening and population effects.

2016, AJ, 151, 167
CEPHEIDS
Cepheides distance measurements are one of the three steps applied
to estimate the Hubble constant. Uncertainties emerging from the accuracy
of the Period-Luminosity (P-L) relation, influence of the metallicity
and reddening directly affects the Hubble constant estimation.

Multiband Cepheid brightness measurements can limit the reddening problem,
and the Baade-Wesselink method contribute to understanding of the physics
underlying Cepheids variables.
2013, ApJ, 773, 69
RED CLUMP
Red Clump stars offer a temptation to significantly decrease
the statistical error
of distance measurements. With the present day
observation methods we can measure mean brightness of the Red Clump stars
with 0.5% precision.

Unfortunately, distances calculated with this technique are strongly affected
by complex population effects. However, this makes Red Clump stars an important
laboratory for our understanding of stellar populations.

2010, AJ, 140, 1038