RX J1856.5-3754

   
3 $\vec {B, R }$, and H$\alpha$ imaging

Images in B, R, and H$\alpha$ of RX J1856.5-3754 and its environment were taken for us in the nights of 2000 April 30, May 1, May 2, and May 3, at Unit Telescope #2 (Kueyen) using the Focal Reducer/Low Dispersion Spectrograph FORS2. The standard resolution collimator was used, and a Tektronix CCD detector with $2048\times2048$ pixels of $24 \,{\rm\mu{}m}$. The corresponding plate scale is $0\hbox{$.\!\!^{\prime\prime}$ }2 \,{\rm pixel^{-1}}$.

During all nights the seeing was good, varying between 0 $.\!\!^{\prime\prime}$55 and 0 $.\!\!^{\prime\prime}$8. The nights of 2000 May 1 and May 2 were photometric, the night of April 30 mostly clear. Clouds appeared during the second half of the night of May 3, which includes the time used for RX J1856.5-3754; from the count rates, however, it appears that the clouds did not affect the observations. In total, ten series of images were taken of RX J1856.5-3754 (see Table 2). Nine were in the order B, R, H$\alpha$, R, H$\alpha$, R, and one - used to fill up time - was shortened to B, R, H$\alpha$, R. Of the latter, the B-band image has much worse seeing and is not used. The total exposure time is about 21 min in B, 1 hour in R, and 5 hours in H$\alpha$. During the photometric night, several standard fields of Landolt (1992) were observed. No useful separate H$\alpha$ calibration images were taken.

RX J1856.5-3754