The time evolution of HH 1 from four epochs of HST images
  We present an analysis of four epochs of H$\alpha$ and [S II]
$\lambda\lambda$ 6716/6731 HST images of HH 1. For determining proper motions
we explore a new method based on analysis of spatially degraded images obtained
convolving the images with wavelet functions of chosen widths. With this
procedure we are able to generate maps of proper motion velocities along and
across the outflow axis, as well as (angularly integrated) proper motion
velocity distributions. From the four available epochs, we find the time
evolution of the velocities, intensities and spatial distribution of the line
emission. We find that over the last two decades HH 1 shows a clear
acceleration. Also, the H$\alpha$ and [S II] intensities have first dropped,
and then recovered in the more recent (2014) images. Finally, we show a
comparison between the two available HST epochs of [O III] $\lambda$ 5007 (1994
and 2014), in which we see a clear drop in the value of the [O III]/H$\alpha$
ratio.
