This is a correct solution. The route that I can verify was a bit different: Octal -> morse gives you text that's interpretable as hex codes. Convert hex codes to text and you'll get even more morse, and once that morse is fixed to use / as separator instead of \ it will give HIDDEN DEEP WITHIN as the plaintext. I interpreted the downloaded image as a hint that you need to collage the numbers into trigrams, and that led me down a rabbit hole where I ended up coding custom code that led me obviously nowhere, so I'm kind of disappointed this is the real method.
