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

Calculating dependencies ... done!
Dependency resolution took 1.11 s (backtrack: 0/20).

[ebuild  N     ] sci-astronomy/wcstools-3.9.7::gentoo  8450 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-libs/cfitsio-4.7.0:0/10-r1::gentoo  USE="bzip2 -curl -test -tools" 2113 KiB
[ebuild  N     ] sci-astronomy/montage-6.1::gentoo  USE="-doc" 43971 KiB

Total: 5 packages (5 new), Size of downloads: 54633 KiB