I want to learn the basics of radiative transfer for my reasearch, which is on planetary sciences. I am looking for a book that would give me the basics of radiative transfer (the mathematics involved) so that I can perform numerical modeling of the radiative transfer process in planetary atmospheres and upper surfaces. I started with the book Spectroscopy and Radiative transfer of Planetary Atmospheres, but I feel it is a bit to difficult for me to catch up. I need something like a primer on this subject.
Chandrasekhar's book is anything but suitable for beginners.
Rob Rutten's course on radiative transfer is classic in the field of stellar atmospheres. It is available here: https://robrutten.nl/rrweb/rjr-pubs/2003rtsa.book.....R.pdf
Dullemond's course covers slightly different areas and it is more introductory: https://www.ita.uni-heidelberg.de/~dullemond/lectures/radtrans_2017/