Mosaic_CCD_en

A new CCD camera system for HIDES, which uses mosaicked 3 EEV CCDs (EEV 42-80), is now open to visiting observers.

Currently, the CCD with the fewest bad columns is placed at the center of the 3 CCDs, and the one which had been used in the former CCD camera system is now placed at the bluer side and the remaining one with some blots on the surface at the redder side. Each CCD has two readouts. Measured properties of the 6 readouts of the CCDs are summarized as follows.

Gain : 2.5-3 e-/ADU
Read-out noise : < 5e-
Bias level : ～500 ADU

Things to be kept in mind for observers are as follows:

Instantaneous wavelength coverage is tripled, 3750A with the red cross disperser and 2340A with the blue cross disperser. However, vignetting is present at the ends of each echelle order in the longest-wavelength portion.
Full frame read-out time is roughly halved to about 50 seconds.
Spectral sensitivity has changed little.
The gap between adjacent CCDs is 500 um, which corresponds to 37 pixels. This results in a loss of 1 echelle order in the recorded spectrum.
On-chip binning is not available yet.

When preparing an observing proposal, please consult "HIDES Quick Observing Recipe", while keeping the above mentioned points due to the mosaicking in mind. Any questions are welcome on the mosaicked CCD camera. Please feel free to send them to izumiura @ oao . nao . ac . jp.

CCD †

Table 1:The measured properties of the HIDES CCDs. Each CCD has two output points.

	Left	Right	Left	Right	Left	Right
	Gain (e/ADU)		Readout noise (ADU)		Bias (ADU)
Red (EPO)	2.6729	2.5633	1.8300	1.9396	487.1	517.1
Green (LUM)	3.0267	2.9428	1.5486	1.4552	513.3	522.7
Blue (MEI)	2.7054	2.6876	1.7529	1.7183	501.8	538.6

Fig. 1: The image of Th-Ar comparison spectrum. Overscan and gain are corrected (large size image).

Linearity †

HIDES CCDs show the good linearity up to around 20,000 ADU. When we fit counts (ADU) with the function of T (exposure time in sec.), Const.*(T^a), a is 0.999 +/- 0.007 (ave.).