5. Previous V 1794 Cyg photometry

The previously published photometry of V 1794 Cyg in our Table 4 consists of the standard Johnson UBVRI photometry of Paper  II and the UBV(RI)_C photometry by Heckert & Stewart (1992). These are discussed separately in Sects. 5.1 and 5.2. The first part of the APT photometry in Dempsey et al. (1992) was already published in Paper  II. The numerical values of the second part of these APT data are published for the first time in our paper (i.e. the APT photometry for B.W. Bopp in Sect. 6.1). Hence the data in Dempsey et al. (1992) are referred to "This paper'' in our Table 3. Apart from Rodono & Cutispoto (1992), our Table 4 contains all V 1794 Cyg photometry published before 1995.

1. UBVRI photometry in Paper  II

Table 3 gives the original reference of each SET in Paper  II (Bopp 1982; Bopp et al. 1983; Kaluzny 1984; Nations & Seeds 1986; Huovelin et al. 1987; Paper II). Our LTM-correction for the three C₁ in Paper  II was: First, the "original'' $\Delta m_{{O}-C_1}$within each SET were obtained from the magnitudes of V 1794 Cyg (Paper  II: Table 2) by subtracting the earlier C₁ magnitudes (Paper  II: Table 1). Then, the weighted UBVRI means of each C₁ from Table 2 of this paper were added to these "original'' $\Delta m_{{O}-C_1}$. For example, the following LTM-correction was applied to the first $V_{{\rm old}, O} = 7.225$ measurement of V 1794 Cyg on HJD = 2442719.5779. The V magnitude for SAO 50313 was $V_{{\rm old}, {C_1}} = 6.653$ in Paper  II. The weighted mean in our Table 2 is $V_{{\rm new}, {C_1}} = 6.636$. Hence the first line in our Table 4 has

This particular LTM-correction is small ( $0\hbox{$.\!\!^{\rm m}$ }017$). But the LTM-corrections  are larger for subsets with SAO 50205 as C₁: $\sim~0\hbox{$.\!\!^{\rm m}$ }05$, $0\hbox{$.\!\!^{\rm m}$ }04$, $0\hbox{$.\!\!^{\rm m}$ }04$, $0\hbox{$.\!\!^{\rm m}$ }02$ and $0\hbox{$.\!\!^{\rm m}$ }03$ in UBVRI, respectively. This is partly due to the BVRI magnitudes of 16 Cyg B (Moffett & Barnes 1979) that were used in Paper  II to determine the brightness of SAO 50205 during SET=28. Another reason for this large LTM-correction was the inaccurate differential UB magnitudes of SAO 50205 minus SAO 50313  during SET=38 of Paper  II, which have been excluded from our Table 2. On the other hand, the LTM-corrections in UBVR for subsets with SAO 50313 as C₁were between $0\hbox{$.\!\!^{\rm m}$ }01$ and $0\hbox{$.\!\!^{\rm m}$ }02$. Finally, SET=2 (C₁: SAO 50260) required a LTM-correction of only $0\hbox{$.\!\!^{\rm m}$ }01$ in BV. Some minor corrections were made to the photometry of Paper  II. Three possibly erroneous observations were excluded: the two V magnitudes on HJD = 2446308.8667 and 2447320.8750, and the B magnitude on HJD = 2447439.7549. In addition to these, flares were identified in four subsets of Paper  II (Col. 8 of Table 4), but these will be discussed in Paper  III (Sect. 3.1).

2. UBV(RI) _C photometry in Heckert & Stewart (1992)

Heckert & Stewart (1992) obtained differential UBV(RI)_C photometry of V 1794 Cyg during 1990 and 1991 (SET=51 and 68). Their C₁ and C₂ were SAO 50313 and SAO 50326, respectively. The standard Johnson UBV magnitudes of V 1794 Cyg were obtained by adding the SAO 50313 values from our Table 2 to the differential magnitudes. The Cousins R magnitudes were transformed into the standard Johnson system (Bessell 1979). The Cousins I could not be transformed, because the I magnitude of C₁ (SAO 50313) is unknown.