X-ray emissions from clusters are most likely originated from a thin hot plasma in a collisional ionization equilibrium. The optical depth of continuum component is order of 10–3, whereas that of emission lines is around unity. Present emission models used for spectral fitting can not estimate this effect, so that the determination of elemental abundances seems to include large uncertainty. The high resolution spectroscopy with ASCA gives a clue to investigate the physical state of hot intracluster gas and a impact to reconsider the basic atomic processes. This is important issue to deeply understand the structure, formation and evolution of clusters, and the origin of intracluster gas.

The EUV emission from hot interstellar plasmas is observed by normal incidence telescopes on board a sounding rocket. It was performed on January 29, 1995, to observe the sky area around the HZ 43 close to the north galactic pole. The wave bands (δλ ~ 10 Å) are provided at 130 and 170 Å by the multilayer coating on the reflectors of 20 cm in diameter and of 30 cm in focal length. The focal plane images are detected by Csl coated MCP’s. The observed flux of HZ 43 is 1.5 counts s−1 at 130 Å and 3 counts s−1 at 170 Å. The diffuse emission is 27 c/s/deg2 at 130 Å and 20 c/s/deg2 at 170 Å. Those preliminary numbers are subjects to change along with the data analysis.

We observed the Cygnus Loop with Gas Scintillation Proportional Counter (GSPC) on board Tenma satellite. GSPC has an energy resolution two times better than that of a proportional counter (PC). Fig. 1 shows the spectrum with the crosses being the pulse height data with ± 1σ statistics. Superposed upon the data point is the best fit model spectra folded through the detector response.