The Mosaic-1 and Mosaic-2 imagers are wide-field optical imaging cameras built for use at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory. These two cameras are nearly identical, but do differ in some respects. The operation of each of these cameras (Mosaic-1 at the KPNO 4m and WIYN 0.9m; Mosaic-2 at the CTIO 4m) also differ in some specifics. This manual contains much information that is common to both cameras, but is focused on the specifics of using the Mosaic-1 at the KPNO 4m and WIYN 0.9m
General Characteristics:
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Arrays: |
8 2048x4096 SITe CCDs; thinned , science grade |
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Image size: |
8192 x 8192 @ 16 bits, plus header, overscan:~135 Mbytes |
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Pixels size: |
15-um (0.26"/pixel at the 4-m; 0.43"/pixel at the 0.9-m) |
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Read-noise: |
~6 e- |
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DQE: |
86% peak at 6500Å (average for 8 CCDs; see also Figure 3.1.2) |
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Dark-current: |
~5 e-/pixel/hr |
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Read-out time (including overhead): |
2 minutes 34 seconds (1 min 6 sec when binned 2x2) |
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CCD Gaps: |
~0.7 mm (~50 pixels) in rows; ~0.5 mm (~35 pixels) in columns |
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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% |
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Filters: |
5.75"x5.75"; parfocal,34 filters now available at KPNO (a list of all available filters can be found here http://www.noao.edu/kpno/mosaic/filters/filters.html) (UBVRI; see Sec 2.6) |
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Saturation: |
Typically, linear to 0.1% to 70,000 e- |
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Gain: |
~3 e-/ADU |
KPNO Mayall 4-Meter Parameters:
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Count Rates: |
At UBVRI=20th mag: U: 35; B:330; V: 340; R: 410; I: 225 e-/sec |
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FOV: |
36'x36', XIMTOOL Orientation: North- left, East-down |
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Scale: |
0.26"/pixel at center; decreases quadratically by 6.5% out to corners |
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Image quality: |
PSF quite constant across the FOV, but ~6% larger in linear scale at the corners |
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Artifacts: |
Faint ~2600-pixel wide image of the pupil in each image (~1% at UI, 0.8% at BVR, 2-4% in narrow-band filters). |
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Typical focus: |
-9900 at ~17C (-10200 for U; approximately -300 unit offset for U-band); change with temperature: -90 units per degree C |
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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. |
WIYN 0.9-Meter (formerly KPNO 0.9m) Parameters:
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Count Rates: |
At UBVRI=20th mag: U: 2; B: 14; V: 15; R: 16; I: 9 e-/sec |
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FOV: |
59'x59', XIMTOOL Orientation: North-left, East-up |
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Scale: |
0.43"/pixel |
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Image quality: |
PSF fairly constant across the field, but a 20-30 focus unit tilt is present. |
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Typical focus: |
31000 at 10C (31050 for U); change with temperature +80 units per degree C. |
Data Acquisition: Acquisition commands are given on computers named rush (at KP4m) or rust (at W0.9m). These computers are currently accessed by the user via a VNC display on tan (at KP4m) and emerald (at W0.9m).
Data Reduction: At the KP4m images can be inspected and processed using the computers tan or nutmeg. At the W0.9m this work is done on emerald.
All the Commands That Are Likely To Be Needed
Observing Commands -- on Rush (at KP4m) or Rust (W0.9m)
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observe |
take one or more exposures prompting for the exposure type |
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doobs |
a script which takes flats/objects for a list of filters |
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mosdither |
takes (typically 5) dithered images in a single filter to fill the gaps in array |
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more |
take more exposures just like the last one |
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test |
take a test exposure. The output image, test, is overwritten each time |
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object |
take one or more object exposures |
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zero |
take one or more zero (bias) exposures |
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dark |
take one or more dark exposures |
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dflat |
take one or more dome flats |
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sflat |
take one or more sky flats |
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focus |
take a focus frame |
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recover |
recover data (if possible) following a crash of the DCA during readout |
Exposure Control Commands
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pause |
pause exposure (e.g. clouds) [do not ABORT or STOP from within pause!] |
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resume |
Resume a paused exposure [then ABORT or STOP if necessary!] |
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tchange |
increase or decrease the exposure time |
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stop |
stop an exposure (and sequence of exposures) reading out the detector |
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abort |
abort an exposure (or sequence) discarding the data |
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pictitle |
Change the title of the picture |
Quick-look and Taping Commands -- on Tan (at KP4m) or Emerald (W0.9m)
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Mscdisplay |
display an entire mosaic frame |
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Mscexamine |
general tool for examining images |
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Mscwfits |
write mosaic frames to tape in multi-extension FITS format |
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Caution: Tape
your data as you go; DLT-7000 (~250 images/tape) and Exabyte drives (~35
images/tape), and DDS-4 DAT drives (~145 images/tape) are available. On nutmeg (KP4m) it takes the following
times to write/read images using mscwfits: DDS-4 DAT 49/54 sec, Exabyte
You can purchase DLT, DAT and Exabyte tapes as well as DVDs (DVD-R 4x) at the Kitt Peak Administration office, but bringing your own is cheaper.
Calibration data:
If you wish, take darks matching
expected exposure times, although we have not measured significant dark current
with the current version of the instrument.
Take dome flats and/or twilight flats (night sky flats work even better!)
Take zeroes (i.e., biases) -- Darken the dome for
darks and zeroes!