Title text:
I'm trying to buy a gravitational lens for my camera, but I can't tell if the manufacturers are listing comoving focal length or proper focal length.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3182/
How to say you're from the US without saying you're from the US. Sorry, man.
Please accept this hug from an internet stranger that is likely heading down the same road... hoping the symptoms end up being a huge nothingburger, but if not then I'm going to miss my hobbyist equipment.