Solar Eclipse Simulator Updates

I’ve just pushed some updates to the solar eclipse simulator that is included in our iOS app. Here are the main changes:

  • Fixed the playback speed adjustment buttons
  • Added a 10s rewind button
  • Added optional Solar Physical Ephemeris display (more below)
  • Layout improvements

This is live now - you don’t need to update your app to see these changes. Just exit and reopen the simulator, if needed.

Controls Changes/Fixes

The ×1, ×5, ×100 buttons can now be tapped while the simulation is playing and the speed will update immediately.

Additionally, there is 10s rewind button just to the right which will immediately set the clock back by 10 seconds - this is useful for replaying the moments around key contact times.

Solar Physical Ephemeris Data

As discussed in the forum post Solar North vs Earth North Graph, I’ve added some additional optional data for the Sun.

Tap the Sun icon towards the left to show/hide this data (it’s off by default). When enabled, you’ll see the following values:

  • q, the solar Parallactic Angle
  • P, the Sun’s Position Angle
  • S(P), the supplement of the Sun’s Position Angle (kinda - 360° minus P, rather than 180° minus P)

These values can be useful in somewhat specialized circumstances.

Changes in the Parallactic Angle, q, will tell you how the Sun’s disc is rotating with respect to you the observer. This is nicely explained here. It can be helpful in determining how any visible sunspots will change position over the course of the partial phases of the eclipse, and so can help you determine where they might emerge as the Moon moves away after C3.

The Position Angle, P and its supplement are useful if you are using an equatorial mount and wish to rotate your camera to a certain orientation relative to the Sun’s north pole. Given that the shape of the corona tends to extend further in either a N-S or E-W direction depending on the current solar cycle, you can use this data to align your camera such that its widest field of view is likely to be aligned with the most extended areas of corona. This can help to avoid inadvertently clipping the corona, while still maximizing your focal length to capture greatest detail. See
the discussion with @whitacre.rick and @dsjohnstonwv here for more details.

I’ll have to back port these changes into the web app, which may take a few days. However, with the eclipse fast approaching, I’m guessing usage is going to start to skew towards mobile in the coming days!