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IMACS Calibrations

Imaging 

 

In the table below we provide some reference numbers of imaging flat counts obtained in the various filters and suggested lamp intensities (Ql and Qh refer to the Quartz lamps in the DCU). These frames were obtained with the dome closed at night. 


Note: During daytime the dome is not completely light tight and the exposure times should be kept <10sec in order to minimise fluctuations due to stray light:


Camera f/2 :


Filter Counts (Fast bin1x1) Exposure time (sec)  Voltage (V)
  Bessel - B         33000           5      Ql
  Bessel - V         32000           6      3.0
  Bessel - R         32000           2      2.5
  CTIO - I          32000           3      2.0
  sloan - g         29000           5      3.5
  sloan - r         27000           3      2.5
  sloan - i         27000           3      2.0
  sloan - z          30000           2      2.0

 


Camera f/4 :


Filter Counts (Fast bin1x1) Exposure time (sec)  Voltage (V)
  Bessel - B         34000           4      Qh
  Bessel - V         27000           6      4.0
  Bessel - R         27000           4      3.0
  CTIO - I          28000           4      2.5
  sloan - g         29000           5      Ql 
  sloan - r         30000           2      3.5
  sloan - i         30000           5      2.5
  sloan - z          32000           4      2.5

 
Flats of the sloan-u are not possible with current lamps (120sec with Ql+Qh give ~7000counts). For this filter twilight flats should be obtained. 

 

 

Spectroscopy

 

Camera f/2 :

The following exposure times will give between 20000-25000 counts using the Qh lamp in the DCU and the Spectroscopic2 filter 

Grism/Slit 0.7" 0.9" 1.2" 1.5" 2.5"
 150_10.8  3sec  2sec   1.5sec  1sec  1sec*
 200_15.0  3.5sec  3sec  2sec  1.5sec  1sec
 300_17.5  7sec  5sec  4sec  3sec  2sec
 300_26.7  5sec  4sec  3sec  3sec  2sec
 
*for 30000 counts - for less counts with slit 2.5" you need to use Ql and (5sec would give ~22000counts) . 

 

Camera f/4 :

The following exposure times will give between 13000-17000 counts using the Qh + Ql lamps in the DCU 

 
Grating (tilt) /Slit 0.7" 0.9" 1.2" 1.5" 2.5"
 150-3.4 (3.4)   11sec  9sec  7sec  5sec  3sec
 300-4.3 (6.0)   40sec  30sec  20sec  16sec  12sec
 600-6.54(8.0)   sec  sec  sec  sec  sec
 600-8.6 (9.3)  80sec  60sec  50sec  40sec  25sec
 600-13.0 (14.0)  50sec  35sec  25sec  20sec  15sec
 1200-17.5 (19.0)   300sec  250sec  150sec  125sec  90sec
 1200-26.7 (27.32)   100sec  85sec  60sec  50sec  35sec
 1200-26.7 (33.5)  120sec  100sec  70sec  55sec  40sec
 1200-32.0 (32.2)   sec  sec  sec  sec  sec
 
 
 

 Examples of flat field images for both cameras and both imaging and spectroscopy can be found in: 

/Volumes/DATA_BAADE/IMACS/CALIB

In the same folder images for all long-slits are also available, although it is recommended to take new images of the long-slits you intend to use at least once at the beginning of your run.  

 

 

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