After a week of cold southerlies and rain, last night was beautifully clear. While walking up to the house I noticed that Jupiter about to crash into the moon. It was something I wasn't expecting and came as a very pleasant surprise. The 80 mm was hurriedly set up and I glued my eye to the eyepiece as Jupiter was slowly occulted by the moon. The mountainous nature of the edge of the moon was clearly visible. Nice!
But it all happened just too fast. Thinking about it afterwards, I wish I had been more observant regarding the occultations of the moons of Jupiter. In the occultation of stars by the moon, the star is extinguised more or less instantaneously, at least as seen by the human eye (notwithstanding the ringing pattern produced by diffraction at the edge of the moon, which may be measured photometrically). But what happens with Jupiter's moons. They have a finite size which might result in them slowly fading from view. The rate of fade will of course depend on the angle at which they approach the surface. The more the angle approaches a graze, the longer the fade will be.
But is this so? Is the response of the human eye fast enough to see this? Has anyone out there observed this? If so I missed it ... next time I will be more observant. Anyone?
Anthony
But it all happened just too fast. Thinking about it afterwards, I wish I had been more observant regarding the occultations of the moons of Jupiter. In the occultation of stars by the moon, the star is extinguised more or less instantaneously, at least as seen by the human eye (notwithstanding the ringing pattern produced by diffraction at the edge of the moon, which may be measured photometrically). But what happens with Jupiter's moons. They have a finite size which might result in them slowly fading from view. The rate of fade will of course depend on the angle at which they approach the surface. The more the angle approaches a graze, the longer the fade will be.
But is this so? Is the response of the human eye fast enough to see this? Has anyone out there observed this? If so I missed it ... next time I will be more observant. Anyone?
Anthony
