The Ebre Observatory is located in Roquetes (Baix Ebre), on the top of a small hill 50 m above sea level. Its coordinates are: Geograhic Latitude 40º 49' 14'' N., Geographic Longitude 0º 29' 36'' E.

Part of the activity of the Ebre Observatory is focused on the solar photospheric observation, taking an image of the Sun every day, weather conditions permitting. This new bulletin is a summary of the observations and measurements made from 1 January to 31 December 2021. During 2021, we recorded 218 images, which were measured by our algorithm, which represents 60 % of the days. Since 1943, Wolf's number, the hemispheric separation (North and South), and their difference (N & S) heve been calculated at the Ebre Observatory.

This bulletin presents the data in a graphic format, with a monthly table and a solar image for each day. Those days which are not on the table are days without observation.

For the daily observation of the solar photosphere we have a Zeiss APQ 150/1200 telescope with a resolution of 0.7 arcsec and an IDS digital camera with 2048 x 2048 pixels. The pixel size is 5.5 x 5.5 μm. The image is captured using software provided by the digital camera manufacturer. The image is then processed using software developed at the observatory. Therefore, for each image, the number of groups (G), the number of spots (q) and the Wolf number (W=10*G + q) are determined. For each spot we mesure,among other parameters, its size in number of pixels, its area in millionths of a hemisphere, and its grey level. The heliographic latitude and longitude, its area, the number of spots in the group, and the group class are determined. A parameter related to the quality of the image, ranging from 1 to 5, is also given.

The daily image of the Sun is available on our website at www.obsebre.es