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Biases and Darks
SUSI_img_cal_Dark

• exposure time = 0 seconds for biases
• exposure time > 0 seconds for darks

The NTT CCD page has more information and a history describing the RON, Gain and Bias levels for each of the SUSI chips.

Download a standard Bias OB and Dark OB here. These ascii files can be imported directly into your P2PP and edited as required. Alternatively, view the parameters needed for P2PP at SUSI_bias.jpg and SUSI_dark.jpg. In these examples, the bias OB takes 9 biases in 2x2 binning mode and without windowing. The dark OB takes 1 x 1800 second dark exposure in 2x2 binning mode and without windowing.

Super Flatfields

• The size of the jitter should be of the order of 2 times the largest object in the field.
• If your object is very large, consider moving the object from chip to chip after each exposure, as one would "nod" the telescope for Infra-Red observations.
• The jitter pattern should be chosen depending on the total number of exposures of each field
• Remember there is a vertical gap between the chips (i.e. never do an offset only along the y axis)
• For a small number of exposures, a tilted grid (???) gives good results.
• For a larger number of exposures, consider moving the telescope in a "star-like" pattern, with all the positions falling on a circle (typical radius = 15"). An even better alternative is to take the offsets at random within a disk of radius ~15"

Sky Flatfields
SUSI_img_cal_SkyFF

Note: SUSI2 has a significant baffling problem, with the largest contribution coming from the baffling of M3. This technical report describes the problem in more detail. The result is that there is a bright region in the flatfield images which rotates with the rotator. To achieve the best possible flatfield, we suggest that you take skyflats for each filter at several rotator positions (0, 90, 180, 270) so that this can be averaged out.

Within the template, one needs to define:

• Number of Exposures: How many flatfields you would like in this filter
• Intensity Level: How many counts do you want in your flatfields?
  Note: default is 30000 counts for Service Mode observations
• Filter: Which filter you wish to calibrate Telescope RA Offsets and Telescope Dec Offsets How many arcseconds in each direction would you like to offset between flatfields?

• takes a 1 second exposure and reads out the SUSI2 chips
• calculates the peak count level in that exposure
• calculates the exposure time necessary to reach the required number of counts
• If the required time is < 0.5 seconds, it will tell you the sky is too bright and ask whether you want to abort the OB or keep trying
• If the required time is > 0.5 seconds, it will display the exposure time it plans to use and asks whether you wish to continue or abort
• takes the requested number of exposures, offsetting the telescope in between each one so that the stars do not lie on the same pixels and can be averaged out
• telescope returns to original position

Download a standard Skyflat OB here. This ascii file can be imported directly into your P2PP, duplicated and edited as required. Alternatively, view the parameters needed for P2PP at SUSI_skyflat. In this example, we are taking 5 skyflats in the V filter with a maximum count level of 30000. We are moving the telescope by 10 arcseconds in both RA and DEC between each exposure, binning the CCD 2x2, and not windowing.

Dome Flatfields
SUSI_img_cal_DomeFF

Note: SUSI2 has a significant baffling problem, with the largest contribution coming from the baffling of M3. This technical report describes the problem in more detail. The result is that there is a bright region in the flatfield images which rotates with the rotator. To achieve the best possible flatfield, we suggest that you take domeflats for each filter at several rotator positions (0, 90, 180, 270) so that this can be averaged out.

Within the template, one needs to define:

• Number of Exposures: How many flatfields you would like in this filter?
• Intensity Level: How many counts do you want in your flatfields?
  Note: default is 30000 counts for Service Mode observations
• Filter: Which filter you wish to calibrate

• takes a 1 second exposure and reads out the SUSI2 chips
• calculates the peak count level in that exposure
• calculates the exposure time necessary to reach the required number of counts
• takes the requested number of exposures

Download a standard Domeflat OB here. This ascii file can be imported directly into your P2PP, duplicated and edited as required. Alternatively, view the parameters needed for P2PP at SUSI_domeflatflat. In this example, we are taking 3 domeflats in the V filter with a maximum count level of 30000. We are binning the CCD 2x2 and not windowing.

Focusing
SUSI_img_cal_TelFocus

Within the template, one needs to define:

• Number of sub-exposures: How many exposures do you want to define the focus sequence?
• Exposure time: How long you want each exposure to be?
  
• Filter: Which filter you wish to focus in?
• Telescope Focus Offset: How many encoder units do you want to move M2 by between each exposure?
• Telescope Offset: How many arcsec do you want to move the telescope by between each sub-exposure?
• Direction of Telescope Offset: Do you want to move the telescope in RA or DEC?

P2PP panel with example parameters

The above example shows a through-focus sequence consisting of 9 sub-exposures, of 15 seconds each, taken through the V filter. M2 is moved by 0.03 focus units and the telescope is offset by 10 arcsec in RA between each sub-exposure. NOTE: You must put the RA and DEC of where you would like to perform the focus sequence in the OB itself.

Send comments to : ls-susi Last modified: Wed Nov 05 2003