These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.12 s (backtrack: 0/20).

[ebuild  N     ] sci-libs/fftw-3.3.10-r1:3.0/3::gentoo  USE="openmp threads -doc -fortran -mpi -test (-zbus)" CPU_FLAGS_X86="avx avx2 fma3 sse sse2 -fma4" 4047 KiB
[ebuild  N     ] dev-lang/cfortran-20210827-r1::gentoo  USE="-examples -test" 101 KiB
[ebuild  N     ] virtual/fortran-0-r1::gentoo  USE="openmp" 0 KiB
[ebuild  N     ] sci-astronomy/wcslib-8.3-r1:0/8::gentoo  USE="tools -doc -fits -fortran -pgplot -static-libs" 3170 KiB
[ebuild  N     ] sci-libs/cfitsio-4.7.0:0/10-r1::gentoo  USE="bzip2 -curl -test -tools" 2113 KiB
[ebuild  N     ] sci-astronomy/cpl-7.3.2:0/26::gentoo  USE="threads -doc -gasgano -static-libs" 3362 KiB

Total: 6 packages (6 new), Size of downloads: 12791 KiB