tokens: and in quiescence, along with their rates of change. We have also refined the supercycle length (and possible changes in superoutburst occurrence rate). The structure of this paper is the following: Sect. 2 presents details about observations, data reduction, and photometry analysis. Section 3 contains information about the photometric behaviour of the system and a thorough study of positive and negative superhumps. We discuss this information in Sect. 4 and present a summary of our campaign dedicated to MN Dra in Sect. 5 . 2. Observations and data reduction The observational data of MN Dra presented here were collected throughout three observation campaigns. The first data were obtained during 6 nights from 2009 October 12 to October 22, in the Skinakas Observatory, Greece. At that time, the star was in a quiescent state. The second campaign was conducted during 15 nights from 2013 July 09 to September 10. On that occasion, data were gathered in Poland, at the Borowiec station of the Poznań Astronomical Observatory, at J. Kochanowski University in Kielce, and at the Ostrowik station of the Warsaw University Observatory. During the 2013 campaign we detected two superoutbursts of MN Dra. The longest campaign was organized in 2015, from June 4 to December 18. Data covering 84 nights of observations were collected at the Borowiec Station, in Pisa in Italy, at Antelope Hills Observatory and at the MDM Observatory in the USA. Once again, two superoutbursts in MN Dra were observed. In Table 1 we present the journal of CCD observations of MN Dra. In total, the star was observed 374.37 h, and 8717 useful exposures were obtained. To summarize, eight telescopes with diameters ranging from 0.25 to 1.30 m were used to collect data during the 2009, 2013, and 2015 campaigns. All data of MN Dra were gathered in a clear filter (“white light”). This approach allowed us to obtain reliable photometry around 18–20 mag when the object was in quiescence. Bias, dark, and flat-field correction of raw files was made in a standard way. For the data reduction we used the IRAF package. The profile (point-spread function) photometry was obtained with the DAOPHOTII package ( Stetson 1987 ). Relative unfiltered magnitudes of MN Dra were derived from the difference between the magnitude of the star and the mean magnitude of two comparison stars marked as C1 and C2 in Fig. 1 , where the map of the observed region is shown. The equatorial coordinates of comparison stars C1 (, , mag in filter) and C2 (, , mag in filter) were taken from the 2MASS All-Sky Catalog ( Cutri et al. 2003 ). Instrumental magnitudes were transformed into the passband, which is very close to observations made in white light. Fig. 1 Finding chart with the position of MN Dra marked as V1 and two comparison stars C1 and C2. The field of view is about . 3. Light curves 3.1. Global photometric behaviour Fig. 2 Global photometric behaviour of MN Dra. For convenience, we use only a day number HJD-2 450 000 [d]
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