Examples of Distance & Angle Measurement
The examples below show the effect of centroiding the starting and ending positions of the Distance & Angle measurement. In each case, the mouse pointer was pressed or released intentionally off the center of the two point sources.
The first picture below shows no centroiding. The starting and ending points are taken literally where the mouse button is pressed and released. Notice that the positions do not "lock on" to the two bright stars.
The next picture shows centroiding on the starting point. When you begin to move, Mira automatically locks onto the centroid point.
The next picture shows centroiding on the ending point only. Mira takes the starting point literally and locks onto the ending point at its centroid position, instead of where you release the mouse button.
The last picture shows the effect of centroiding both the starting and ending points. Mira locks onto each centroid positions after you press and release the mouse.
The 4 measurements from above are tabulated below in the Distance Measurements window. Notice that this image does not have a WCS Calibration, so the distance and angle are reported in units of pixels and trigonometric angle. If it did have a WCS calibration, distance and angle would be reported in arcseconds and position angle and the endpoints X1, Y1, X2, and Y2 would be reported in right ascension and declination rather than column and row coordinates.
