Arrays:

8 2048x4096 SITe CCDs; thinned , science grade

Image size:

8192 x 8192 @ 16 bits, plus header, overscan:~135 Mbytes

Pixels size:

15-um (0.26"/pixel at the 4-m; 0.43"/pixel at the 0.9-m)

Read-noise:

~6 e^-

DQE:

86% peak at 6500Å (average for 8 CCDs; see also Figure 3.1.2)

Dark-current:

~5 e^-/pixel/hr

Read-out time:

2.6 minutes

CCD Gaps:

~0.7 mm (~50 pixels) in rows; ~0.5 mm (~35 pixels) in columns

Cosmetics:

Good to excellent: typically 2 bad columns per CCD, but many 2-8 pixel areas of 5% variation (flatfield completely) and some very large areas of 10% variations that all flatfield to <0.5%

Filters:

5.75"x5.75"; parfocal, 26 filters now available (UBVRI; see Sec 2.6)

Saturation:

Typically, linear to 0.1% to 70,000 e-

Gain:

 ~3 e^-/ADU

Count Rates:

At UBVRI=20th mag: U: 35; B:330; V: 340; R: 410; I: 225 e-/sec

FOV:

36'x36', XIMTOOL Orientation: North- left, East-down

Scale:

0.26"/pixel at center; decreases quadratically by 6.5% out to corners

Image quality:

PSF quite constant across the FOV, but ~6% larger in linear scale at the corners

Artifacts:

Faint ~2600-pixel wide donut ghost (~1% at UI, 0.8% at BVR, 2-4% in narrow-band filters).

Typical focus:

-9900 at ~17C (-10200 for U); change with temperature: -90 units per degree C

ADC:

Atmospheric Dispersion Correction: For broad-band filters, use ADC in "track mode" with appropriate filter selected. For flat-fields and narrow-band exposures, use the "null" position or closest broad-band filter mode in wavelength.

 Count Rates:

At UBVRI=20th mag: U: 2; B: 14; V: 15; R: 16; I: 9 e-/sec

 FOV:

59'x59', XIMTOOL Orientation: North-left, East-up

 Scale:

0.43"/pixel

 Image quality:

PSF fairly constant across the field, but a 2-3 focus unit tilt is present.

 Typical focus:

4410 at 10C (4413 for U); change with temperature +1.8 units per degree C.

observe

take one or more exposures prompting for the exposure type

doobs

a script which takes flats/objects for a list of filters

mosdither

takes (typically 5) dithered images in a single filter to fill the gaps in array

more

take more exposures just like the last one

test

take a test exposure. The output image, test, is overwritten each time

object

take one or more object exposures

zero

take one or more zero (bias) exposures

dark

take one or more dark exposures

dflat

take one or more dome flats

sflat

take one or more sky flats

focus

take a focus frame

recover

recover data (if possible) following a crash during readout

pause

pause exposure (e.g. clouds) [do not ABORT or STOP from within pause!]

resume

resume a paused exposure [then ABORT or STOP  if necessary!]

tchange

increase or decrease the exposure time

stop

stop an exposure (and sequence of exposures) reading out the detector

abort

abort an exposure (or sequence) discarding the data

pictitle

change the title of the picture

mscdisplay

display an entire mosaic frame

mscexamine

general tool for examining images

mscwfits

write mosaic frames to tape in multi-extension FITS format