Narrow-band filler photographs of comet TSK were taken in the light of C2, CN and C3 by Rahe McCracken and Donn, have been analysed in terms of Haser's model of the coma. The isophotes obtained from these photographs were corrected for sky background. The isophotes were circularly symmetric. Radial intensity profiles were obtained along the sunward, antisun and the two perpendicular directions. In each case, these profiles were the same within the experimental errors in intensity (±5%).

Theoretical curves based on Haser's model were computed for different combinations of the parameters β0 and β1 where l/β0 is the scale length for the decay of the unobserved parent molecule and 1/β1 the corresponding quantity for the observed daughter molecule. A comparison of the theoretical and observed intensity profiles, yielded our best estimates for β0 and β1 for the different molecules. These are listed in Table 1. In some cases, we were able to obtain lower limits only to the ratio β0/β1 because the isophotes do not go out far enough, a limitation caused by the sky background. It is to be noted that the same values of the parameters were obtained from observations on different dates indicating no unusual activity in the comet in the intervening period. We believe ours is the first result ever obtained for C3.

In Table 2, we summarize all the results for C2 and CN in different comets. It appears that the scale lengths differ between comets, a result which cannot be attributed to different helio-centric distances alone.