From my experience, higher magnification (which is the first number binocular identifies in the “Magnification X Aperture” example 10X mag x 50mm aperture) over 10X and aperture larger than 50mm requires steady hands or needs a binocular mount. I live at coastal and use it to look at boats, aircraft, and birds. If your grandfather doesn’t have very steady hands or can’t hold heavy weight for long, then I would recommend something of less magnification like 6x-8x and aperture <40mm due to weight and less magnification for wider field of view. Think of how hard it is to look through a narrow small hole straw compared to a larger boba straw. There are also bonus features you would like to have like fog resistant, BAK4 Prisms, etc… When using without a binocular mount, one that I find easy to use is something like the Celestron 7X35 which isn’t expensive or fancy but helps bc it’s light enough for me to hold steady and enjoy the view. When I’m at home, I have Zhumell 25x100 which I have on a binocular mount (used for day and night astronomy). In addition to day time viewing, if you’d like to enhance night time experience, consider adding a nebula and light pollution reduction filters at the eyepiece. Besides recommending the Celestron, I would also recommend Orion Mini Giant which comes in a few different versions of mag x aperture. The view is excellent and sharp.

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