Let's compute some power spectra! For testing convenience, this package includes the Planck 2018 frequency maps, scaled down to $n_{\mathrm{side}} = 256$. These are not exported by default, so you have to call them with PowerSpectra.planck... names. In this example, we will use the 100 GHz half-mission temperature maps. We also convert from $K_{\mathrm{CMB}}$ to $\mu K_{\mathrm{CMB}}$

using Healpix
using PowerSpectra
using Plots

# retrieve the downgraded planck maps
nside = 256
map1 = 1e6 * PowerSpectra.planck256_map("100", "hm1", "I_STOKES")
map2 = 1e6 * PowerSpectra.planck256_map("100", "hm2", "I_STOKES")
plot(map1, clim=(-200,200))