  We report photometric observations of comet 29P/Schwassmann-Wachmann 1 made
on August 12, 2016 with the broadband B, V, R and I filters and the SOAR
4.1-meter telescope (Chile). We find the comet active at that time. Enhanced
images obtained in all filters reveal three radial features in the 29P/
Schwassmann-Wachmann 1 coma, regardless of the image-processing algorithm.
Using a high-resolution spectrum of comet 29P/Schwassmann-Wachmann 1 reported
by Ivanova et al. (2018) on the same date, we estimate the relative
contribution of the gaseous emission and the continuum to the total response
measured with our broadband B and V filters. The gaseous-emission contribution
appears to be very small 2.5%. We compute the dust production Af\r{ho} in 29P/
Schwassmann-Wachmann 1 for the four filters and find its growth with the
wavelength, from 3,393 cm in the B filter to 8,561 cm in the I filter. We model
the color slope of dust in Comet 29P/Schwassmann-Wachmann 1 using agglomerated
debris particles. Simultaneous analysis of the color slope in the B-R and R-I
pairs suggests a single dominant chemical species of 29P/Schwassmann-Wachmann 1
dust particles consisting of Fe-Mg silicates and obeying a power-law size
distribution with index n=2.55. This conclusion is consistent with the previous
thermal-emission study of 29P/Schwassmann-Wachmann 1.

Earth and Planetary Astrophysics