Comet C / 2021 A1 LEONARD could be visible to the naked eye by Christmas 2021.

 After a last update of the light curve of Comet Leonard, and using only visual observations, it seems that, if there are no surprises, the comet could be visible to the naked eye, my last estimate indicates a probable maximum visual magnitude of m1 = + 4.6 for the date of December 11, 2021, until reaching its perihelion in January 2022, its rate of increase in brightness is quite low, Law Power R ^ -1.7, and n = 4.46, but it is usual for new comets coming from The Oort Cloud, I attach the light curve, but beware, this curve mixes ccd and visual, it is important to differentiate both types of observations, since the difference is usually 1.5 magnitudes, according to a personal study, in this regard, Using the heliocentric and geocentric distances, based on the classic brightness formula for comets, using logarithms for the comet-earth and comet-sun geometry, it could give us a visual magnitude close to +5 and perhaps +4, everything will depend of the act ivity that the comet demonstrates in the determining moments of its proximity to the sun:

m1 = + 8.2 +5 log (D) +4.46 log (R)

This formula is far from the one calculated based on the CCD + VISUAL data, which based on 842 observations would look like this:

m1 = + 11.7 +5 log (D) +5.59 log (R)

The contribution of dust + gas is added in the case of this last formula, we take into account that the spectral response ccd for comets is similar to the amount of dust dispersed and emitted by sunlight, and unlike visual observations, where we observe the swan and C2 bands, and the sum of OH, indicating a small portion of the gas emitted, this leads us to the conclusion that there is more gaseous emission in Comet Leonard than dust.