Top: field of view of our observations. Boxes indicate the approximate positions of the slits of our costumed mask. North points upward while east rightward. Both directions are indicated with arrows. The image was acquired using an R filter (r_G0303). The bright object on the very bottom is Qatar-1, which is indicated with a red box. Bottom: extracted instrumental spectra for Qatar-1 and six reference stars. The different wavelength coverage is caused by the uneven distribution of the reference stars at the sky. In both figures, Qatar-1 is indicated in red color.