The new Meudon Spectroheliograph since July 2017

ANO6/INSU, Observatoire de Paris, LESIA

The spectroheliograph uses a moving lens and a fixed thin slit, so that the surface of the full solar disk is scanned in about 30 seconds. It provides since July 2017 full line profiles (3D files), from which we derive, after data reconstruction, monochromatic 2D images of the photosphere (line wings and continuum), chromosphere (line core) and prominences at the limb (using an artificial moon of neutral density 1 to reduce the light of the disk). Several series are made every day by the observing team. The cadence is convenient to study mid and long term variations, as the solar cycle and the variability of cycles (we have 10 cycles registered in Halpha since 1909, even more in CaII K, as the collection started in 1898). More than 120000 images are available on various supports as glass, film plates and CCD (see the Bass2000 database).
The spectroheliograph has been transformed in 2017; we now offer classical images plus full line profiles (FITS 3D datacubes with standard corrections as line curvature, and RAW TIFF 3D datacubes without any treatment). Line profiles of Halpha (656.28 nm, order 3), CaII K (393.37 nm, order 5), CaII H (396.85 nm, order 5), and Hbeta (486.13 nm, order 4) are fully registered (40 wavelength points for Halpha and Hbeta, 100 points for CaII K and CaII H). The spectral resolution is 0.0100 nm for CaII K and CaII H, 0.0133 nm for Hbeta and 0.0167 nm for Halpha. The spatial pixel is 1.1 arc sec. We show below some examples of Halpha and CaII K data, but CaII H and Hbeta are also available.

Latest images and datacubes, HTTP and FTP services

1 - Principle: spectroscopic scan by moving lens

2 flat mirrors coelostat / moving entrance lens: f = 4 m, diameter 0.25 m + diaphragm 0.14 m (solar image diameter 37 mm)
Spectrograph: slit 1.5" / collimator f = 1.3 m / camera lens f = 0.4 m / grating 300 groves/mm (orders 3, 4 and 5)
Detector: PCO camera sCMOS, 2048 x 2048, 16 bits unsigned integers, 100 frames/s

MPEG movie

Various spectra of CaII K line in facula, sunspot, filament, prominence

2 - Halpha line 656.28 nm step 0.0167 nm

3 - CaII K line 393.37 nm step 0.0100 nm

CaII K and CaII H lines (top: atlas; bottom: spectroheliograph)