Since the division of the Korean Peninsula in 1948, South and North Korea have independently developed their astronomical almanacs: Ryeokseo at the Korea Astronomy and Space Science Institute in South Korea and Cheonmunryeok at the Pyongyang Astronomical Observatory in North Korea. This study compares Ryeokseo and Cheonmunryeok for the year 2015, focusing on publication systems, content, terminology, and differences in data calculation methods. Additionally, it examines the calendars of South and North Korea from 2018 to 2023, analyzing similarities and differences in the representation of calendrical dates, public holidays, and other related aspects. The findings reveal that while the structure and content of the astronomical almanacs are similar in both countries, notable variances exist in the versions of ephemerides, time scales, and calculation precision. Consequently, identical data points are often recorded with slightly different values in each country's almanacs. Furthermore, approximately 28% of the terms used in North Korea's astronomical almanac are either not utilized in South Korea or have different definitions. Regarding calendar systems, those of South and North Korea are largely similar, resulting in no significant discrepancies in dates. However, there are notable differences in the observance of public holidays. While traditional holidays are common to both, most holidays are distinctively celebrated. Notably, North Korea does not observe religious holidays, and many of its holidays are associated with the regime.

We have analyzed 42 research papers regarding on the solar astronomy written by North Korea scientists to investigate the current status of astronomical activities in North Korea. The papers are surveyed from the ‘Bulletin of Astronomy’, the ‘Physics’, the ‘Bulletin of Academy of Science’, and the ‘Natural Science’ in North Korea, and SCI journals. In addition, we refer to the presentation material announced in the 2015 IAU by director of Pyongyang Astronomical Observatory (PAO) and the 2013 OAD/IAU reports. We have analyzed the papers statistically according to three criteria such as research subject, research field, and research members. The main research subjects are the sunspot (28%), observation system (21%), and space environments (19%). The research fields are distributed with data analysis (50%), numerical method (29%), and instrument development (21%). There have been 25 and 9 researchers in the solar astronomy and space environment, respectively since 1995. North Korea’s solar research activities were also investigated in three area: instrument, solar physics, and international research linkage. PAO has operated two of sunspot telescope and solar horizontal telescope for spectroscopy and polarimetry, but there is no specific information on solar radio telescopes. North Korea has cooperated in solar research with Europe and China. We expect that the results of this study will be used as useful resource in supporting astronomical cooperation between South and North Korea in the future.

We have investigated the North Korean astronomical articles published in five media such as the Rodong Sinmun (노동신문), Minju Choson (민주조선), Tongil Sinbo (통일신보), Munhak Sinmun (문학신 문), and Choson Sinbo (조선신보) for 15 years from 2005 to 2019. The astronomical articles were classified by subject to study the astronomical activity in North Korea. We have examined the perceptions of astronomy in North Korean society through the temporal variation of astronomical articles according to four subjects. As a result, we have found that there are many articles in the subject of Historical Astronomy and Astronomical News in the media. In the era of Kim Jong-un, the articles on the Historical Astronomy decreased while the Astronomy news tended to increase. We have also summarized the specific issues and topics including the change of the standard meridian, launch of satellites, astronomical news, and so forth. The North Korean astronomical article is a valuable resource to examine the current status of North Korea's astronomy and astronomical education. We expect the results of this study to be a useful resource in preparing for inter-Korean astronomical cooperation.

We compared and analyzed the astronomy terms currently used by astronomers in the two Koreas to promote inter-Korean astronomy cooperation. We analyzed a total of 2716 pairs of terms common in both Koreas glossaries, using the astronomical terminology contained in the South Korean source, the ‘Terminology of Astronomy’, and the North Korean source, ‘Mirror 2.0’. For each pair of terms, their morphological features and meanings were compared. We categorized into 11 groups for comparison of astronomical terms. We found that most of the terms are used similarly in the two Koreas. About 47% of the total is similar in form. Although terms are different, meanings communicate about 37% of the total. As a result, similar terms used by the two Koreas correspond to about 85% of the total. However, 15% of terms are difficult to understand because they have different forms or meanings such as diffraction (회 절/에돌이), flare (플레어/요반) etc. Further research on terms that are used differently by the two Koreas, and the conversion of appropriate terms through mutual understanding should be made in the future.

We have estimated the fractal dimension of the molecular clouds associated with the H ΙΙ region Sh 156 in the Outer Galaxy. We selected the 12CO cube data from the FCRAO CO Survey of the Outer Galaxy. Using a developed code within IRAF, we identified slice-clouds (2-dimensional clouds in velocity-channel maps) with two threshold temperatures to estimate the fractal dimension. With the threshold temperatures of 1.8 K, and 3 K, we identified 317 slice-clouds and 217 slice-clouds, respectively. There seems to be a turn-over location in fractional dimension slope around NP (area; number of pixel) = 40. The fractal dimensions was estimated to be D = 1.5 ∼ 1.53 for NP ≥ 40, where P ∝ AD/2 (P is perimeter and A is area), which is slightly larger than other results. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Fractal dimension is apparently invariant when varying the threshold temperatures applied to slice-clouds identification.