“The [Afrho] parameter and the cometary activity. The [Afrho] parameter is a parameter defined by A’Hearn et al. (1984) to measure the activity of comets. This parameter is proportional to the dust “filling factor”, the ratio of the integrated cross section of the dust particles and the projected surface of the diaphragm in the field of view. The use of this parameter will be discussed. Simple ways of calculating it from calibrated CCD images of comets will be explained and illustrated with examples. The total magnitude depends on the diaphragm used and the wavelength and is a mix of dust and gas emissions. Afrho allows the monitoring of the dust emission rate of comets, dust properties through reddening and the gas to dust ratio.
We estimated the comet Afrho and water production rate for comet C/2022 E3.