It is so big because it is based on Latex and its ecosystem, which is on most distributions by default quite large. It will install a lot of Latex packages which you probably won't need right away, but if size isn't a big problem I wouldn't bother with trimming it down.

One of the advantages of Lyx is that it builds on Latex and its extensions, which thanks to tens of years of development is very mature and feature rich. If something that you want to do with Lyx isn't supported you can just use raw (La)tex script. For example I used it for autonumbering of chemical compounds.

Most of the dependency weight is due to -doc packages. For example, `texlive-latex-extra-doc` is a 325MiB download.

Here's a (partial) listing of the dependencies that were automatically selected sorted by download size†:

https://www.dropbox.com/s/950vm93v1ncna6x/lyx_synaptic.png?d...

So you can avoid a lot of your disk space usage by excluding‡ the -doc packages.

†: I haven't figured out how to get Synaptic to show estimations of unpacked sizes on a per-package basis

‡: In aptitude, `- .*-doc` I think?

It's the TeX distribution, it has loads and loads of packages. It's better than having to download single packages on demand.

You can try adding --no-install-recommends which gets it down to 55 MB, though I balked when it asked me if I wanted to install unauthenticated packages.

That sounds like a local caching issue — an `apt-get update` first usually fixes that for me.

Or, you have a third-party APT repository specified in `/etc/apt/sources.list{,.d/*}` that you didn't install the keys for.

Or the NSA.