CALWELL
LUNAR OBSERVATORYCALWELL
LUNAR OBSERVATORY(This page is under construction, but as the real time images are A FIRST for lunar eclipses, I have decided to make some of these available through these pages NOW).
Introduction
Real time images were down-loaded from URL http://200.133.12.33 during the actual eclipse of 1996 September 27.
The observations were made from Olinda, Pernambuco State, Brazil at station:
Latitude: 08 o 03' 00" S Longitude: 34 o 53' 14" W Altitude: 0 m Weather conditions: (Partially) Cloudy
The images are the work of Jose Amaury Pereira and Jose Fernando Tepedino and their team who captured the eclipsed Moon on 27 September in Olinda-Pernambuco State from Brazil. The equipment was adapted to the CCD Camera of the Federal University of the Pernambuco system. Jose Amaury Pereira is an associate member of the SAR (Astronomical Society in Recife) and SAF (Astronomical Society of France).
A Sony IRIS CCD camera was used on a driven Refractor Telescope of 60 mm diameter (aperture), focal Length of 400 mm, focal Ratio f/6, with an ND-4 filter on top and the Sony Iris CCD camera at the main focus. An Equatorial Fraunhofer Mount with clock-drive in right ascension was used with manual declination axis adjustment and with the mount positioned North - South.
A set of the images have been down-loaded and analysed to determine the size of the umbral shadow and hence, to detect change in its geometry during the eclipse.
The images are now available from URL:
Remember that the timing information on each image is not very precise, because it was based on a computer clock (and the WinSNTP software didn't work in the slow connection established).
All the captured images (23M bytes, about 400 images) are available individually at the above URL
This experimental project was developed by professors Pereira and Tepedino, at the Espaco Ciencia Museum, at Olinda, Brasil, together with people from the local Amateur Astronomical Center (the CEA - Centro Estudantil de Astronomia).
The software for capturing images was developed at the Departamento de Informatica - Universidade Federal de Pernambuco, which also supported the work.
provides a brief description of the experiment which includes equipment and software details and links to developers, supporters and participants. The URL is:
Image Analysis
Twenty two of these images have been analysed using image analysis techniques to determine change in the geometry of the umbra during the eclipse. One of the real-time captured image is shown below to generally illustrate the image quality.
The results of the umbral measurements taken from these images are included in the report below:
Introduction
Real time images and video records of several lunar eclipses have been measured by image analyst techniques to determine the geometry of the umbra. As these images are topocentric, a procedure has been developed to compute the expected topocentric umbral size for each observing site from geocentric data. These values are compared with the measures made of the umbral image on the moon to detect any change in the size of the umbral shadow during the total lunar eclipse of 1996 September 27.
The images yielded the best results from image analysis when they were converted from colour to grayscale and processed with Photoshop Version 3.0 using Image/Map/Invert, Image/Adjust/Brightness-Contrast (with contrast increase to 50%), Filter/Noise/Despeckle and Filter/Sharpen/Sharpen Edges.
Two typical images are shown below, the first as captured by the team and the second after Photoshop processing prior to measurement.
The measurements provide a comparison with the topocentric umbral semi-diameter (Fi) computed for the observing site (the method is described fully in my web page concerning a similar analysis for the partial lunar eclipse of 1996 April 3-4). The data revealed a small change in umbral size during the eclipse as presented in three Excel plots below:
The images analysed show some scatter in umbral semi-diameter measurements (Ru), particularly after totality. However, a change in the size of the umbra is clearly established with an increase of + 0.15 degrees before totality and a decrease of - 0.2 degrees after totality. These values are of a similar magnitude to that found for the partial lunar eclipse of 1996 April 3-4 and establishes that the technique of image analysis and umbral measurement can detect change in umbral geometry during these eclipses.
Conclusion
This result confirms that the height of the Earth's thermosphere changes over the period of each lunar eclipse studied, as seen by the departure of measured umbral size to that expected from the topocentric computations for several observing sites.
© Michel Benvenuto - September 1996
Three of these images have been processed by Photoshop Version 3.0 for image measurement. They were converted to grayscale from colour, processed by unsharp masking and edge sharpening before measurement. The best fit circles for lunar and umbral semi-diameters from the image analysis are shown in Figure 10 and are compared with the computed topocentric umbral radii (Fi) expected from Michel's site, in Figure 11.
