How to add PHP to a node without php filter? I have a one-off page on my site (webcam), where i need to run some php to eg. calculate today's sunrise time, add a daylight image at night, etc.

I understand PHP Filter is a security risk, and not recommended if it can be avoided.

My page is actually a panesl page, so not neccessarly a node.

I thought maybe i could do the coding and (some) content in a node template, or what other options do i have? A module? Sounds heavy... In my theme's php?
What are pro's and con's?
It really depends since you're planning to add functionality then the best place would be a module but if you're altering HTML or basically the output and maybe quite a little raw data manipulations then that could be in your theme.

Mostly a basic question that needs to be asked is, do you want the "thing" to be functional when you turn off or change your theme? If yes then that would give a strong idea that you would be creating a custom module.

For adding PHP code with panels, you can create custom panel panes. For nodes, your can use blocks or hook_preprocess_node() to add your code in the node level.