Varese 0.84m telescope
The Varese 0.84m telescope, operated by Società Astronomica Schiaparelli , is located on the top of mount Campo dei Fiori, 1226 meters above the sea-level in the pre-Alps (longitude E8° 46' 11.7" — latitude 45° 52' 06.0"), opened in 2018, has a classic Cassegrain design on a fork mount, and two focus stations are available (Cassegrain F/20, Newton F/3.3) with automated switching. It is operated both from the observatory and remotely. The telescope has unobstructed access to any position on the sky, with a limit of 10deg on the height above the local horizon (which permits reaching -34deg in declination on the meridian).
An Astrolight Echelle multimode spectrograph is mounted and always available at the Cassegrain focus. It can be rotated to any angle, with the slit usually oriented along the parallactic angle for optimal flux calibration. It can be used both in echelle and long slit mode. The Echelle grating is an R2 79 ln/mm, and the cross-dispersion is achieved by a N-SF11 glass 60 deg prism. Gratings available for low resolution single dispersion are 600 l/mm (blaze 500 nm) and 830 l/mm (blaze 850 nm)
The slit can be widened continuously from 40micron to 300micron (usually set at 180micron=2.5 arcsec). The slit is viewed by a ASI 120M CCD camera, which allows both on-slit and off-slit auto-guiding. In echelle mode, a resolving power of 12,000 is obtained with a 180micron slit width, and 15,000 by closing it to 100micron which is a fair match to the 1.5 arcsec seeing that the telescope enjoys on good nights when the atmosphere is steady.
| grating | blaze | scale | usual recorded |
|---|---|---|---|
| ln/mm | (Ang) | Ang/pix | range (Ang) |
| 600 | 5000 | 2.3 | 4100-8600 |
| 830 | 8500 | 1.5 | 5800-8900 |
| 79 | echelle | 0.15 | 4230-8900 |
The CCD camera is a SBIG ST10 XME with KAF-3200ME front illuminated chip with microlenses for increased QE, with an active pixel matrix 2184x1472 corresponding to 10.0 x 14.9 mm, pixel size 6.8x6.8 micron, Peltier cooled to -40 °C (from ambient temperature), readout noise 10 e- rms, gain 1.5 e-/ADU, and a dark current (@-30°C) 0.001e-/pix/sec. The chip size allows to cover the normal operating echelle range of 4230-8900 Ang without gaps in wavelength among the 27 Echelle orders.
Low and high intensity beams illuminating a dome screen are used for flat-fielding, while for wavelength calibration a HCL Thorium[Ar] lamp is adopted. A decker behind the slit allows to select the length of the long-slit, with 15arcsec avoiding overlap of adjacent orders.
