European Southern Observatory New Technology Telescope

General :
Observations :
Operations :

Night Operations

Flat Fielding. 
--------------

Keep the level of the flat fields with the dome lamp switched on
to less than 5000 counts.

Be careful with adjusting the voltage of the Variac. It does not take
much to reach 5000 counts.

If one is not taking dome-flats, pull the plug out of the power
supply socket. It may be that there is still some light produced 
by the lamp even though the voltage of the Variac reads zero.

Focus Wedge
------------

To get consistent results with the focus wedge, do the following.

i) Preset the telescope to a star which has a magnitude near 12.5

ii) Start the template, but do not press OK. Typically DIT=2 and 
NDIT=5. Always use the focus wedge with the large field objective 
and the Ks filter.

iii) Set the RTD to display individual DITs. Store a fixed pattern.

iv) Offset the telescope by 50 arcseconds. Make sure that the five
images
of the star are clear of any other images, whether they be positive or
negative.

v) Set the RTD to display the INT frame.

vi) Once a full frame has appeared (wait for the green symbol to appear
twice), press OK and select the central object.

vii) Check that the computed offset is reasonable. If it is
reasonable select yes, if not select no. 

viii) If the offset is less than 0.01, there is no need to select
another object. If it is larger, select another object. This can be
the same object as before. Wait for the green symbol to flash twice,
press OK, and select the central object again.

ix) Repeat vi) vii) and viii) until the offset is less than 0.01.

x) Set the RTD to display individual DITs.

Focus Sequence
--------------

On some occasions the focus sequence is more convenient. This is
true if the field is crowded.

To run a focus sequence, do the following.

i) Load the template SOFI_img_cal_TelescopeFocus.seq. The sequence can 
be run with any filter and any objective.

ii) Start the template, but do not press OK. Set DIT=2, NDIT=5. It
does not have to be these values, but one should intergrate for at
least 10 seconds to average out seeing effects.

iii) Set the RTD to display individual DITs. Store a fixed pattern.

iv) Offset the telescope by 50 arcseconds.

v) Set the RTD to display the INT frame.

vi) Once a full frame has appeared (wait for the green symbol to appear
twice), press OK and select an object that is clear of other objects.
Do not select objects with a peak flux above 15,000 counts.

vii) The template will now run and compute the FWHM of the selected
image.
The FWHM is displayed in the message window of Bob. At this point in
time we do not compute the focus offset, so you will have to note
which image was in focus and change the focus accordingly.

viii) Set the RTD to display individual DITs.

Presetting near the moon
------------------------

If it is possible that the telescope preset could pass in front of the
moon,
then put SOFI into DARK mode and preset manually from the TCS. Recall
that SOFI has no shutter.
  

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