skycalc is an R package: a wrapper for the AA+ library for implementing Jean Meeus' Astronomical Algorithms. AA+ was written in C++ by PJ Naughter. The Latest Version is available at: http://www.naughter.com/aa.html
To install skycalc, please use the following R code:
library(devtools)
install_github("helixcn/skycalc")
If you haven't had devtools installed, please install it by typing "install.packages("devtools")" in R console. On Windows OS, you also need the Rtools being installed, and correctly setup.
Please feel free to send an email to the package's maintainer Dr. Jinlong Zhang if you have any question or comments.