Photometric observations of Main-belt asteroids and Near-Earth asteroids (NEAs), with the mean goal of producing their lightcurves, are carried out with the 77cm Tonantzintla Schmidt Camera of the INAOE. The telescope's current optical system added a field-flattening lens that provide a focal distance of 2135.2 mm, and an image scale of 96.6 arcsec mm-1.
We are using a CCD E2V42-40 de 2048 x 2048 pixeles camera, that produce an image scale of 0.52 arcsec pix-1, and a field-of-view (FOV) of 28.8 x 21.7 arcmin. Selected physical parameters and observational circumstances for the observed objects are shown in Table 1 and Table 2 of this section. To consult the results of the Fourier analysis of lightcurves, please see Table 3 in the section "Data and Results".
The relationship between the diameter and the absolute magnitude H depends on the albedo. Although this relationship is bimodal, with albedo values peaking at 6% and 25%, the average value of albedo appears to be 14%. For an albedo of 0.14, the absolute magnitude H, corresponding to a size of 1km, is H = 17.75. Thus, the relationship between the size and albedo is shown in equation (1) (Harris 2014):
When the albedo of an asteroid is known, the diameter in kilometers, as a function of absolute magnitude H, and geometric albedo pν is given by the equation (2):
The composite lightcurves themselves are available in the same section.Depending on the brightness of observed objects and weather conditions, the typical integration times varied between 30 and 90 s. For each observing run, master bias, dark and flat-field images were produced. Scientific images were corrected for bias, dark and flat-field effects using Image Reduction and Analysis Facility (IRAF) packages.Differential photometry and period analysis were done using {\it MPO Canopus}. In each case, we used four solar analogs non-variable comparison stars, in the same FOV, to generate lightcurves. Comparison stars were selected near the path covered by the asteroids during the night.
Assuming that the lightcurve of an asteroid is produced by a given geometry in rotation, the brightness of an object is proportional to the projected area, and the ratio between the minimum and maximum cross sections (CSmin, and CSmax, respectively) is determined by the peak-to-peak amplitude (A) of the lightcurve through a very simple formulae (Harris, et al. 2014):
In order to resolve the possible ambiguities deriving correct rotation periods of observed asteroids, we used the constraints on amplitude of variation {\it versus} harmonic order of the Fourier function proposed by (Harris, et al. 2014). The Fourier fit used in the composite lightcurve is also shown in Table 2.
The lightcurves show the relative instrumental magnitude {\it versus} the rotational phase, calculated with the rotation periods given in Table 2. The caption of the figures indicates, for each night, the plot symbol used, the UT time of observations, and in addition, the JD for zero rotational phase, and the corresponding phase angle. The zero phase is corrected for the light travel-time effect. Uncertainty bars are plotted for each individual data point. {\it MPO Canopus} Fourier analysis tool provides the period solution, and Fourier coefficients defining the shape of the composite lightcurve for each dataset. The solution also provides the instrumental magnitud offset, between the asteroids and comparison stars, for each individual lightcurve (obtained in different nights), that we used to calculate the peak-to-peak amplitude of the composite lightcurves.
| Number | Name | (UA) | e | Taxonomic class |
H (mag) | Diameter (Km) | Albedo | Commentary |
| (1117) | Reginita | 2.2475 | 0.1983 | S | 11.7 | 10.29 | 0.3516 | Flora family |
| (1363) | Herberta | 2.9036 | 0.0682 | S | 11.3 | 13.91±2.11 | 0.337±0.157 | Koronis family |
| (2434) | Bateson | 3.0796 | 0.1704 | - | 11.4 | 16.75±2.94 | 0.197±0.103 | MB-Outer Asteroid |
| (3775) | Ellenbeth | 2.7862 | 0.1704 | Ch | 12.8 | 17.08±0.08 | 0.024±0.003 | MB-Outer Asteroid |
| (5401) | Minamioda | 2.7997 | 0.1491 | S | 12.1 | 9.68±0.41 | 0.299±0.043 | MB-Outer Asteroid |
| Number | Name | date (UT) | RA (J2000.0) | DEC (J2000.0) | Delta (UA) | r (UA) | (degrees) | V (mag) |
| (1117) | Reginita | 2015 Oct. 4.10 | 23h 04m 02.6s | -10° 28´ 14''0 | 1.013 | 1.956 | 13.73 | 14.0 |
| (1363) | Herberta | 2015 Dec. 15.01 | 04h 08m 052.7s | +20 010 38:000 | 1.996 | 2.945 | 6.18 | 15.6 |
| 2015 Dec. 16.07 | 04h 08m 05.0s | +19 590 23:000 | 2.001 | 2.945 | 6.54 | 15.6 | ||
| 2015 Dec. 17.08 | 04h 07m 18.7s | +19 570 11:000 | 2.007 | 2.946 | 6.54 | 15.7 | ||
| (2434) | Bateson | 2015 Nov. 11.35 | 02h 29m 29.6s | +21 580 34:000 | 2.035 | 3.016 | 3.03 | 15.6 |
| (3775) | Ellenbeth | 2015 Dec. 01.04 | 02h 27m 16.7s | +19 410 17:000 | 1.505 | 2.421 | 11.06 | 16.3 |
| 2015 Dec. 02.07 | 02h 26m 40.0s | +19 410 38:000 | 1.513 | 2.423 | 11.46 | 16.3 | ||
| (5401) | Minamioda | 2015 Nov. 13.14 | 03h 10m 50.4s | +18 500 45:000 | 1.395 | 2.384 | 0.43 | 14.8 |
| 2015 Nov. 21.13 | 03h 02m 39.0s | +18 590 40:000 | 1.403 | 2.382 | 4.12 | 15.1 |