Get time of maximum eclipse & Chart JS update

[johnarban]

This finds the time of maximum eclipse as well as the peak value. It uses slightly better values for the distance (the topocentric distance to the moon provide by astrocalc, and the true distance ot the sun rather than the average distance). Since the Sun is a bit more than 1 AU, the eclipse fraction can be about a percent higher than we currently estimate. this also derives the eclipse peak time and estimates the beginning and end of the eclipse. In all, it takes about 30ms to run, so it is run only when the location is changed. The plot and display I put in are very temporary, and only useful for testing (I don't know if we really want to have a graph or not).

The main goal for this commit is so that the user can easily when the eclipse is. This can then also be used by us to modify the user interface or time controls depending on the phase of the eclipse

[patudom]

Can you remind me how we intend to use this calculation? Is it solely for the purpose of deciding when to slow down time, as discussed in #14?

It looks like there are still round off errors because there is a large margin of places within the totality path where the max % doesn’t quite reach 1. (And it looks like the delta from 1 varies depending on where you are along the totality path):

Also, I was trying to compare the max eclipse times for locations in a chart on this page, but it looks like there may be errors there. For example, if you look at Poplar Bluff, MO, their totality start and max totality times are the same. I would expect max totality to happen ~halfway between the start/end times, which is more in line with what John’s calculation shows, right? Or could their times be correct if the approach to/exist from totality are not symmetrical?

For all the locations I checked, John's "max eclipse time" is within the totality bounds on the chart, so I do think it will serve our purposes if we just want to find some time during totality.

• Is it possible to run a query for whether a selected location is within the shaded eclipse path?

• If so, we can use John’s max eclipse time to figure out internally when to slow down time to show the corona sprite for longer - maybe +/- 10 seconds from John's max time.

• We can also add a button somewhere that says “go to totality” when you are inside the eclipse path.

But we probably don’t want to otherwise display any of this calculated info since it doesn’t always agree with data found elsewhere.

• If that makes sense, we should strip out anything from the UI and internal calculations that we aren’t actually going to expose.

[patudom]

I think this is superseded by #60, so is it ok if we close this, @johnarban?

[johnarban]

it is ok to close

😭

[johnarban]

As a note. this uses an updated version of the Chart JS scatter plot component, with some small usability updates which make a little easier to use.