Fig. 1 Intensity plot of C/2011 L4 (March 3 2013). Numbers indicate intensity levels in greyscale (0 - black ; 255 - white) by Ademir Xavier On last March 3rd I took some photos of C/2011 L4 (Panstars). Here I present an excercise of astrometry using one of those images to extract some meaningful data from this observation. What I do here can be applied to any other comet image or, in fact, celestial object in the sky. My aim is to show a simple example of practical applicaton of mathematics and geometry in the determination of sizes of celestial objects. My interest is: To estimate the apparent (in minutes of arc) and real dimension of the tail (in km or mi) of C/2011 L4; To estimate the apparente (in minutes of arc) and real dimension of the coma (in km or mi); A digital estimate of the comet brightness will not be attempted however, because this would involve a complex process of image calibration. For that aim, we need: Comet image with date; Sca...
Dedicado aos aspectos práticos da astronomia amadora, bem como ao seu ensino e história.