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Do.Lo.Res. successfully refurbished

A completely new acquisition system based on the new generation CCD controller, Acquisition Software, User Interface and a new thinned, back-illuminated, E2V 4240 CCD has been installed in Dolores during May 2007. This upgrade increases the performances of Dolores in terms of system reliability, image quality, readout noise and reading speed.


The reading time of the new ccd controller is now 4.45 µSec/pixel , i.e. about 4 times faster than with the previous controller. The gain is about 1 e- / ADU and the Readout noise is 7 e-. Unfortunately, due to the smaller size of the pixels, the Do.Lo.Res FOV decreased by ˜ 1 arcmin.

Detector Characteristics

Area 2048 X 2048 pixels
Pixel 13.5 µm
Size 27.6 X 27.6 mm
Type Full frame - back illuminated
Scale 0.252 arcsec/pix
FOV 8.60‘ (12.16‘ diagonal)

Binning 1 Output 2 Output
1x1 22 sec 11 sec
1x2 12 sec 6 sec
2x2 8 sec 4 sec
Table1: Reading time of full image vs. binning

Performances

A quick analysis of the calibrated field of GRB070418 (courtesy S.Covino, Brera-INAF) gave a magnitude V˜24.5 with S/N˜3 in 300s exposure and seeing 1.1 arcsec.

The R-band raw zeropoint, as derived from standard stars, is R ˜26.45 (which is very similar to the old-Loral).


Figure1: The GRB070418 field; BVR composite.



Figure2: NGC3982 field; 6x300s R-band. Notice the very good cosmetics of the new E2V chip.

Please note that the calibration of the new E2V chip is still in progress. The refurbishment of Do.Lo.Res is the result of a great joint effort between the Padova-INAF Observatory (cryogenics, mechanics, ccd controllers and final tests), Brera-INAF Observatory (new optics, mechanics), Catania-INAF Observatory (user interface software) and Fundación Galileo Galilei-INAF (ccd controllers, software, optical tests and simulations, final assembling and commissioning).