The photo shows the north-western part of Corona Borealis captured through a 135 mm lens. Below the photo are shown spectra of three selected stars in the field - α, η, and S CrB - captured through a low resolution (R~250) slitless spectrograph (C8-SA100-grism setup - the same configuration detailed here: https://www.astrobin.com/j25tgg/). The spectra are shown corrected for instrument response with selected absorption/emission lines labeled. The three stars display markedly different spectral properties, reflecting variability in their mass, surface temperature, and evolutionary state.

α CrB (also known as Alphecca, Gemma, Gnosia, and Ashtaroth) is the brightest star in Corona Borealis with an apparent magnitude of 2.2. It is a white-blue main sequence or sub-giant A-class star located at a distance of ~75 light years and residing in a binary system accompanied by a much fainter (by a factor of ~100) yellow main sequence star of class G5V. Accordingly, the spectrum of α CrB is dominated by deep, broad hydrogen Balmer absorption lines, characteristic for the early main sequence A-class stars.

η CrB is a close visual binary comprised by two nearly identical yellow-white main sequence stars of spectral class G2V - the same spectral class held by the Sun. The system is located at a distance of ~58 light years, and the two components orbit their barycenter with a period of 42 years. The furthest angular separation during their orbit is around one arcsecond with a current separation of only ~0.5 arcseconds, which would require a higher-powered telescope to resolve. Hence, the spectrum is a blend of the two components.

S CrB is a Mira variable star - a pulsating red giant star - located at an estimated distance of 1300 light years. Its apparent magnitude varies between 6 and 14 (corresponding to ~1000-fold change in brightness) with a period of ~1 year. The spectrum was captured near the most recent maximum (see graph below, courtesy of the Plot-a-light-curve function at aavso.org). Interestingly, the recent maximum was unusually bright, in fact, the brightest in recorded history going back as far as 1864. As is characteristic for stars of the M class, the spectrum is dominated by deep, broad molecular absorptions brought about by titanium oxide, the existence of which is possible in the stellar atmosphere due to the relatively low surface temperature. In addition, the hydrogen Balmer lines are in emission, seen most clearly in this spectrum for the gamma and delta lines.



More information on the recent events of S CrB, including much higher resolution spectra than my simple setup is capable of, can be found in these forum threads:
https://groups.io/g/RSpec-Astronomy/topic/mira_s_crb_at_very_bright/92166720
https://www.cloudynights.com/topic/831073-s-crb-at-record-maximum/