|Format||4K x 4K 15-micron|
|FOV (arcmin)||26.5 x 26.5|
|Pixel size (1x1 binning, arcsec)||0.389|
|Readout modes||full frame, 1 x 1 binning|
|central 2k x 2k window, 2x2 binning|
|Cycle time (readout+overhead; 1x1 binning, s)||28.0|
|Read noise (e-)||7.5 to 8 e- typical|
|Gain (e-/ADU)||1.0 after pipeline processing|
|Dark current (e-/pix/s)||0.002 @ -100 C (estimated)|
Description of Standard filters
LCO has introduced a new readout mode for the Sinistro cameras on the 1-meter telescopes. The mode reads the central 2048 x 2048 pixels, with 2x2 pixel binning, and with a readout overhead of 9 seconds.
Time-sequence observations of bright objects become less efficient with longer CCD readout times and other overheads. An example of a science program that benefits from reduced readout overheads is the observation of planet transits. Also, phenomena that change on time scales on the order of minutes cannot be observed efficiently if the readout overhead is too large. A short readout time will open a window into new science.
LCO has deployed a new CCD readout mode at the 1-meter telescopes where only the central 2k x 2k pixels of Sinistro images are read out, and the pixels are binned 2 x 2, resulting in a 1k x 1k pixel image. To shorten the per-image overhead further, the number of CCD wipes before each exposure are reduced compared to full-frame readouts. The "central 2x2k binned" mode reduces the total overhead from ~28 s per image to ~ 9 s.
The shortened overhead can increase the shutter open time over the duration of an observation, and hence benefits the achievable signal-to-noise. This mode is recommended for the acquisition of time series where:
The new central_2k_2x2 mode is released in shared risk mode. Observers should validate if this new mode is appropriate for their science before committing all allocated time.
In the portal's request composition page, the readout mode is selected from a drop down menu in the Instrument Configuration section.
In the API, include the following statement in the new API language to explicitly select a readout mode:
"mode": "full_frame" || “central_2k_2x2”}]
If no readout mode is defined, the full_frame mode will be used per default.