The x axis is azimuth and the y axis is altitude (elevation). A point represents a post. As an example, this chart represents your post that I am replying to now:

I have circled the current (as of the post) locations of the sun and moon in the sky and shaded the current day and night sides of the earth for context. The sun circle is centered on the point representing this post that I am now replying to. The sun was above the horizon (which would be 0 degrees elevation) and around 160 degrees azimuth - sort of south-south-east as you view it. You can tell it's winter because even though the post took place when the sun was approaching maximum elevation, it was still fairly low in the sky compared to its summertime maximum elevation.

-------- Original Message --------

On February 17, 2018 2:56 AM, Timothy Collinson <xxxxxx@port.ac.uk> wrote:

On 12 February 2018 at 23:01, Caleuche <xxxxxx@sudnadja.com> wrote:

Here's yours:
https://i.imgur.com/lj3jytL.png

You do post up until about midnight (though I am inferring your location as in the UK somewhere),

Yes, south coast of England - opposite the Isle of Wight so right in the middle.

but there's a clear strong band of posts about 2/3rds the way into the evening. You don't post past midnight but start posting fairly early.

The width of the band is, of course, because the elevation of the sun is much higher in the summer than the winter, so you can get a feel of the seasonality of the posting as well.

OK, I thought I understood what I was looking at, but now I'm not so sure. What are the axes?

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