Without login.cl iraf/pyraf does not work properly. Some commands may execute (like zerocombine, ie the binaries) but when the command will need to retrieve some information (like wavelength calibration/plotting, even shell commands like ls ) it will not respond (see error examples below). IRAF: Select a directory (like user’s home) …
Scisoft includes a number of Starlink programs but not all. So perhaps someone (in this case me!) needs to run something that it is not included in the Scisoft (like DIPSO). So, nothing wrong to go on and install both. But in this case that someone has to be careful …
Installing and running Starlink is pretty much straightforward. Firstly, get the latest release (Namaka, when this post was written) and extract the file wherever you want. Then select which shell you want to use and follow the post-installation run-up or the info given below (supposing it was downloaded and extracted …