STUDY OF THE BIPOLAR PLANETARY-NEBULA NGC-2346 .1. HISTORICAL PHOTOMETRY OF THE CENTRAL STAR

This first part of the study of NGC 2346 contains the photometry of the central star in the period 1904-1980 based on 487 plates as well as on UBV photoelectric measurements. After a phase of constant brightness the star declined nearly linearly by about +0.(m)15 between 1955 and 1978. This decrease can be interpreted as an extinction due to dust. Mie measured 34 stars in the vicinity of NGC 2346 in order to extend the sequence of the comparison stars as well as to derive the distance of this object using the reddening-distance method. Unfortunately, the diagram E(B - V) vers. distance shows a very large scatter and it must be considered as inconclusive. As a very preliminary estimate we derived M(V) = +2.(m)7 and a distance of D = 430 pc.