What is purpose of Sunrise button?
It is for building a chart for the moment of sunrise at the given location used by some financial astrologers for daily forecast.

When you click the button, astroclock stops, if it was running, and displays a wheel when the Sun is on ascendant.
Note, that Sun and Asc positions are equal only in case a Sun's disk center used for calculation and a light refraction is ignored. See Upper limb and Refraction settings to control that.

How to read that sunrise chart?
Allegedly, a planetary configuration for sunrise moment may describe a 'potential' for price action. The Moon and its aspects are most important chart elements for interpretation and considered as a financial instrument significator, USD in the case.

Accordingly to those a short or long position has to be opened at the time close to sunrise.
I use the method for trading EUR/USD. Take profit 45...50 pips, no stop loss, a position has to be closed before London session ends.

For example, at March 16, 2015 the Moon in sunrise chart is on the edge of Capricorn and Aquarius, squaring Venus that is also in last 3 degrees of a sign. That might mean a USD weakness for several hours and USD has to be sold in favor of EUR buy.

A next day the Moon in the middle of the sign (~15) and has rather close sextile to Uranus (orb about 8' arc). This is a stronger position and I placed a short order for EUR/USD (bought dollars for euros).

Another example of strong Moon and USD, +73 pips profit.