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Abstract. -We present the results of U B rH αz monitoring of a sample of T Tauri stars. The method of differential CCD photometry was applied. The observations span a range of ten days and show that eleven out of twelve sources varied during this time interval. These variations are correlated in all bands. Periods were detected (confidence level 99.99%) for eight out of eleven variable stars; one additional period was found at the 99.9% confidence level. Of those, one (BP Tau) agrees with previously published periods; two, GM Aur and IQ Tau, do not; six are new detections of periodicities. The sample is drawn from the Taurus-Auriga and Cepheus IV star-forming regions.

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CCD images of comet P/Swift-Tuttle, obtained in April 1994 with the 2.2m telescope at ES0 La Sills/Chile, showed a comaless stellar nucleus. From absolute photometry we estimated the equivalent radius of the cometary nucleus to be about 11 km (assuming an albedo of 0.04 as for P/Halley) for two rotation phase angles which differ by about 75 deg. From that we conclude that the nucleus is either of rather spherical shape or that the viewing geometry was almost pole-on during our observations. An analysis of the plasma tail and inner coma of the comet by means of photographic plates and CCD images through IHW and BVR filters, obtained with the 8Ocm Schmidt camera and the 1.2m telescope at Calar Alto/Spain in November 1992, revealed several tail rays, head streamers and substructures in brightness excess areas in the coma. While some of the tail rays extended to several million km nuclear distance, most of them can be traced to starting points which lie in a region just 20000-35000 km projected distance tailward from the nucleus.