Celestron C11 Edge HD F:10 telescope working at primary focus with a Baader ND-5.0 Solar Screen Filter Mylar sheet + ZWO ASI290MM monochrome camera with Continuum Baader green filter from the terrace of his home in Hospitalet del Llobregat (Barcelona/Spain).
The resulting video record was made in black and white. Subsequently and with the use of the public domain program: VirtualDubMod uses various VDF digital filters (plugins) provided by the program to give: false color, improve contrast, noise removal, etc., in order to obtain a single frame in which you can interpret the “black drop.”
He attached the address where you can find the little traffic video:
Black-drop image by Alfredo Vidal Solar Activity Picture of the Day for November 11th, 2019. “The world wide home of active solar imagers”