Hi Denis – i can’t help with advice on a magnifying ‘screen’ – but windows has an accessibility toll caked Magnifier which can be used to magnify the screen and give a bigger ‘virtual’ screen. I have used ut but found it a bit coarse grained. The MacOS accessibility tool called Zoom i find is a lot better (one of the reasons I mainly use MacOS these days).
Whatever type of computer your friend uses it would be worth looking into the accessibility options for visually impaired.
I also find that a lot of astro programmes often have small controls with lots of options, which make them difficult to use for those with visual challenges.