CFH12K Exposure Time calculator - GUI guide

The way it looks:

Select the parameters by clicking/entering/selecting the fields in black ink in the top portion of the form and then run DIET by clicking on the "RUN DIET" button.

The output from DIET is a simple ASCII format and can be grabed with the mouse and pasted into your favorite editor.

Input fields:
  • Type = Object type:
    • Point Source: stars & QSOs
    • Galaxy: distant compact sources - seeing dominated profile
    • Nearby Galaxy: distant compact sources - object dominated profile
    • Extended Source: uniform illumination over square arcsecond scales

  • Filter = Bandwidth selection:
    Only the B,V,R & I filters are supported but using the level sky field entry, one can constraint DIET to compute numbers for other filters.
    • B
    • V
    • R
    • I

  • Mag. = Object magnitude:
    Magnitude of the object, or class of objects, to observe.

  • SNR = Signal-to-noise ratio on the object:
    The signal-to-noise ratio of the object, or class of objects, to achieve for the magnitude defined in the previous field. Here are typical values required depending on the scientific program. Refer to the documentation for a complete discussion on the subject.
    • SNR = 3 : Detection - Photometry error = 33%
    • SNR = 7 : Fair detection - Photometry error = 15%
    • SNR = 15 : Good detection - Photometry error = 7%
    • SNR = 25 : Quality photometry - Photometry error = 4%

  • #Night = Number of nights for the program:
    The maximum number of nights available can be imposed. If the total exposure time computed by DIET exceeds what can be achieved in the maximum available time including all nights (assuming an object that would go through zenith in the middle of the night
    • #Night = Auto :
    • #Night = {1,2,3,4} :

  • Seeing = Image quality:
  • Sky = Sky brightness:
  • Airmass = Median airmass of the observation:
  • %Atm.Tr. = Atmosphere transparency:

Action fields:

  • Dithering Option ON/OFF = Split exposure time in standard CFH12K blocks:
  • RUN DIET = Execute DIET and display results:
  • Default = Reset all input fields:
  • Documentation = Point to the DIET documentation.
  • Help = Point to this page.

   Comments on the CFH12K pages to Jean-Charles Cuillandre:
   DIET was developed by Simon Kras (CFHT/UVic Coop) and Jean-Charles Cuillandre (CFHT).
   CFH12K is the CFHT CCD wide-field imaging mosaic.