A 50-mm balloon-borne white-light coronagraph: I. Basic structure and experiments on the ground

A 50-mm balloon-borne white-light coronagraph was introduced in the study, which was a traditional Lyot coronagraph, with a working wavelength of 5500 angstrom and a passband of 50 angstrom for observing the inner corona from 1.08 R circle dot to 1.5 R circle dot. Dhyana 95V2-YNTT sCMOS was used to collect the observational data. Three experiments were conducted on the ground. The first experiment was conducted at the Gaomeigu Station, Lijiang, Yunnan, and the other two were conducted at the Wumingshan mountain in Daocheng, Sichuan, approximately 4800 m above sea level. The data with scientific significance were obtained in the latter two experiments. Comparison of our data with those obtained by the K-cor of the 20-cm aperture of the High Altitude Observatory at the Mauna Loa Solar Observatory on the same days verified the consistency of the two datasets, indicating the successful development of the white-light coronagraph. The brightness of the background sky indicates that Wumingshan is an ideal high altitude site for solar observations.