How To Post An Image With An Autoconverting Url?

I wanted to link to an external image located at an address with the string "NGC" (lowercase) in the URL. In preview, the string autoconverted to uppercase, which broke the image link. I hadn't checked but suspect that the same thing would happen in the actual post.

How do I enter such an image into a post? I vaguely recall a recommendation on how to non-convert to the effect of "put it into code tags", but 1) it might not work as an image URL if I do that, and 2) I don't know how to do that anyway.