Digimizer - my new measuring eng

Digimizer - my new measuring engine

by the Theodore Lunar Observatory 2006 July 17

Introduction

Here is one example of the Digimizer© measuring capability using one of my digital images from the total lunar eclipse of 2004 May 4. This has been pasted to a suitably larger scale dark image so that the center of the umbra best fit circle is well within the composite image.

Figure 1

Procedure

Step 1 : Calibrate the image of the eclipsed Moon by a best fit circle and straight calibrator line (both in blue) set to the semi-diameter of the Moon at mid-eclipse (0.275°) as shown in the box and the Measurements list.

Step 2 : Find the grey scale contours at the umbra edge using the magic wand tool set at a line separation of 2, in red.

Step 3 : Find the best fit circle and its center to this umbra edge, in green.

Step 4 : Measure the umbra radius and read the values in the provided  box or Measurements list as  the measured umbra semi-diameter (Fi) of 0.731°. This is just slightly smaller than the expected mid-eclipse value of Fi = 0.7627°.

Figure 2

Further Images

In Figure 2 an image outline and the umbra profile found (in blue) of the partial lunar eclipse of 2005 October 17, has been pasted over Figure 1, calibrated to 0.268° for the Moon  and the umbra measured as 0.734° in red (the expected value was 0.7334°). Note that the values shown for the 2004 May 4 image are no longer relevant as they have been changed to the new calibration for 2005 October 17.

Additional Attributes

Captured images of the eclipsed Moon can be acquired from my input cameras such as the Meade Lunar & Planetary Imager (LPI), Canon IXUS still digital camera and Panasonic NV-GS15 Digital Video camera.

The quality of the composite image is good if kept to its original size as captured by <Alt> < Prnt Scrn> to the clipboard.  The Digimizer format (*.dgz) is much stronger and clearer in colour than if converted to *.jpg or *.gif .

The web site for the Digimizer© software can be found at http://www.digimizer.com/

Produced by the Theodore Lunar Observatory Australia 2006 July 17