Working at the observatory.
For the capture of the spectra analysed for “Music from Light” we have counted on the support and equipment of Astrogirona, Girona Astronomical Association. We have used telescopes and cameras located in the observatories “Can Roig MPC C99”; “Albanyà MPC L17” and also Rafael Balaguer’s observation equipment. The observations have been made in Llagostera, Albanyà and Rocafort in Catalonia, Spain, and also in Glendo, Wyoming, USA.
The telescopes used have been a Takahashi Mewlon, a magnificent Cassegrain reflector with Dall-Kirkham optical design, 210mm in diameter and 2415mm focal length, f/11.5; a Meade LX200 ACF, an aplanatic Schmidt-Cassegrain catadioptric, 254mm in diameter and 2500mm focal length, f/10; and a 406mm diameter, 3251mm focal length Meade ACF, f/8. Advanced Coma Free (ACF) equipment combines multiple technologies to produce highly proven distortion-free images with true colour image delivery across their entire flat field of view. Exceptionally, a Fuji Finepix S7000 bridge camera was directly used as an optical system to capture the solar corona spectrum of the solar total eclipse on August 21st, 2017 from Glendo, Wyoming, USA; and the spectrum of the earthshine on the Moon from Rocafort, Catalonia, Spain. The telescopes have been used on the computerized mounts Gemini G42, Meade LX200 SmartMount, Skywatcher EQ8, and 10Micron GM3000 HPS.
Various cameras have been used to capture the images, the one already mentioned Fuji Pinepix S7000; and the following have been used connected to telescopes: QHY5 colour, CMOS; QHY9 monochrome, CCD; ATIK 16IC colour, CCD; Philips Toucam Pro II Colour, CMOS and Moravian G4-9000 Mono, CCD. CCD cameras are much more sensitive and suitable for studying weaker, more distant objects, such as stars or nebulae. CMOS, with their lower sensitivity, are more often recommended (because they become less saturated and allow long video exposures) for the observation of brighter and closer objects, such as the Moon, the Sun, and the planets, as well as some comets.
To break down the light of the stars and obtain their spectra we have used low-cost and affordable systems for any astronomy enthusiast. The main device is a Paton Hawksley Spectroscope Star Analyser 100 diffraction grating, which features a high-efficiency design with 100 lines/mm. This is the most important element of the assembly needed to capture the spectra. It is an optical component with a regular pattern, which diffracts (divides) light into several beams. The direction of these beams depends on the spacing of the grating and the wavelength of the incident light, so the grating acts as a dispersive element. It is directly screwed into the coupling of the cameras to optical systems, either a telescope or a photographic lens.
The chemical elements found in the studied stars produce mostly absorption lines, so to know their chemical composition we can determine the wavelength of the absorption bands.
Here we share the analysis of the spectrum of the comet C/2014 Q2 Lovejoy, with the detection of water.
You can listen to our sonification of this comet in “Music from Light”, track 16 “Lovejoy”.