The 20-cm refraction equatorial telescope was used for sketch observation of a sunspot till 1998. As a technical staff engaged in solar sunspot observation, Tanaka stood by even not only in the time of fine weather but in few intervals of clear weather, doing sketch observation of this sunspot for a long time.
Although his technique sketched with the pencil the sunspot of the solar image with a diameter of 25 cm projected on the projection version, even if it was at the fine weather time, the perseverance and technique of sketching the place of the good image one by one, and obtaining an image sharp as a whole were required for it.
He published the paper about observations repeatedly with his fellow researcher, especially the one published in 1960 was very important on solar physics which was introduced to the scientific journal of each country, capturing the spotlight from the astronomy community in the world.
Tanaka was reportedly employed by the Observatory since the personnel for a sunspot sketch those days were needed. He was then studying painting under a prominent painter.
Tanaka often thronged the laboratory, talked by writing and argued those days in front of the blackboard which was placed in each laboratory.