tokens: Fig. 1 were obtained with the 1.6-m telescope of the National Laboratory for Astrophysics (Brazil) on 2011 May 31 (Ivanova et al. 2018 ). The instrumental setup and data processing are presented in detail in Cavichia, Costa Maciel ( 2010 ) and Ivanova et al. ( 2016 ). Table 1 summarizes the characteristics of our observations: the date of observation (the mid-cycle time, UT date), the geocentric ( ∆ ) and heliocentric ( r ) distances, the phase angle of the comet ( α ), the position angle of the extended Sun–comet radius vector ( φ ), the filter (photometry) and grid (spectroscopy), the total exposure time during the night ( T exp ), and the mode of the observation. Table 1. Log of the observations of comet 29P/Schwassman–Wachmann 1. 3 MORPHOLOGY OF THE COMA As can be seen in Fig. 1 , the λ4277/39 Å filter transmits the radiation of CO + ions and the continuum, whereas the transmitted radiation flux through the λ5309/169 Å filter may truly be considered as the continuum, without CO + ions. Thus, to derive the pure ion image, we subtracted the composite image of the continuum that was obtained in the SED537 filter from the combined CO + image, controlling the particular light transmission of each filter and various continuum levels. We used values of reddening obtained from the spectral observations of comet 29P presented by Korsun et al. ( 2008 ) and Ivanova et al. ( 2016 , 2018 ). The images of the comet in the two filters were centred using the central isophotes, which was closest to the maximum brightness of the comet. The panels on the left of Fig. 2 present the intensity maps of the isolated CO + coma after subtraction of the continuum intensity from the observed intensity in the CO + band, and the panels on the right present the images of the dust coma of comet 29P. Figure 2. Isolated CO + (a, c, e, g) and dust (b, d, f, h) coma of comet 29P derived from observations on November 8, 2007, December 4, 2008, March 29, 2009 and December 26, 2009. All images are scaled to erg cm −2 s −1 Å −1 . The values near the white contours, corresponding to the column density at a cometocentric distance about 20 000 km, are presented in Table 2 . The sunward (⊙), north (N) and east (E) directions, and the cometary motion vector (V) are shown. The isolated CO + coma is clearly observed on all the dates of observation presented here (see Fig. 2 ): it is compact, asymmetric relative to the optocentre, and always elongated in the sunward direction, although this elongation does not coincide exactly with the direction to the Sun. The CO + coma observed on 2007 November 8 was only slightly elongated in the sunward direction, while on 2008 December 4 the comet had a very compact and strongly elongated CO + coma in the solar hemisphere to at least 60 000 km. On 2009 March 29, the comet had a small asymmetric coma with strong sunward elongation. In contrast to the CO + coma, the dust coma, formed by sunlight scattered from dust particles, was more extended and
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