2 Observations and data reduction

  Narrow-band images (H$\alpha$ and [O III] $\lambda$ 5007Å) of eight PN (Table 1) have been taken with the 2.2 m telescope and CAFOS (SITe-1d CCD, 2048 $\times$ 2048 24 $\mu$m px, 1 px = $0\hbox{$.\!\!^{\prime\prime}$}53$ projected at the sky) at the Calar Alto observatory (only MWP1) in August 1996 and with the 1.54 m Danish telescope and DFOSC (LORAL/LESSER CCD, 2052 $\times$ 2052 15 $\mu$m px, 1 px = $0\hbox{$.\!\!^{\prime\prime}$}39$) at ESO (ESO No. 61.C-0101) in July 1998.

  

Table 1: List of our observed PN. The field sizes (fs) of the images shown as well as the measured angular nebula diameters (faintest visible part of the main nebula on the H$\alpha$ images) d in West-East ($d_{\rm WE}$) and North-South direction ($d_{\rm NS}$) are given. $^\star$: For the elliptical nebulae MWP1 and NGC1360 the diameters are given for their axis in NW-SE/SE-NW direction. The exposure times (t in sec) were the same for both the H$\alpha$ as well as the [O III] $\lambda$ 5007Å images. In the case of A43 two H$\alpha$images were taken and co-added. The figure numbers (F) refer to the figures in this paper. All PNe are shown with North up and East left on a linear intensity scale

A search for PN around hot (pre-) white dwarfs had been performed in October 1997 at ESO with the 1.54 m Danish telescope and DFOSC (ESO No. 60.C-0376). H$\alpha$images with an exposure time of one hour had been taken. A list of observed objects is given in Table 2.

For the data reduction we used IRAF (Tody 1986). All images were flatfielded using suitable sky flats.