WORKING WITH TAURUS
revised 04/09/98
TAURUS is a wide-field imaging Fabry-Perot interferometer designed
to obtain spectra over a field of up to 9 arcmin with a resolving power
anywhere between 2,000 and 100,000. Its main use is in measuring
velocity fields of extended emission line objects - HII regions, planetary
nebulae, supernova remnants and galaxies.
A TAURUS spectral scan normally consists of a large number (typically
100) of separate 2-dimensional images taken sequentially at different gap
settings of the Fabry-Perot etalon, each giving a two-dimensional image
in a different wavelength bin. By stacking these together it is possible to
build up a 3-dimensional spectral line datacube.
STARTUP PROCEDURE
TCS:
TAURUS has successfully been used with the ALPHA TCS. The focal setup
must still, however, be typed in by hand
- USER> STATION CASS
- USER> INSTRUMENT TAURUS
- USER> AGSELECT CASS
- Zeroset AZ and ALT
to zeroset on the targets switch to computer control:
- USER> AZ 298
- USER> ALT 89
- USER> ENG
- USER> ZERO AZ TAR
- USER> ZERO ALT TAR
Drive AZ and ALT slowly in + direction over the zeroset target points,
then switch to computer control again
to zeroset absolute:
- USER> ZERO AZ ABS
- USER> ZERO ALT ABS
Zeroset absolute will go wrong in case an absolute encoder bulb is broken!
When slewing to the first object check azimuth and altitude incremental and
absolute encoders are in close agreement and updating.
- USER> ZERO ROT ABS
- USER> WAVELENGTH 0.6
- USER> TEMP ...
- USER> PRESS ...
- USER> HUMI ...
- USER> CAL LAST
AUTOGUIDER:
Autoguiding is done using the CASS autoguider. GSS for finding
guidestars, ICL>prag x y for moving the guideprobe to the required
position. (Remember to configure GSS as gss>con wht taurus)
TV:
Use Direct mode (AGCOMP) to acquire objects as slitviewing is not
possible.
PREPARATION PROCEDURE
Telescope focus:
The best telescope focus is determined by taking short exposures on the CCD.
Last focus value: 96.9mm (04/09/98)
Calibrate procedure:
The best (only) way to determine the rotator center and performing the
calibrate procedure is by using the TV Direct Viewing mode (acquisition
mirror in by typing ICL>AGCOMP). Proceed as usual. Last RotCen:263, 275
(scanswitches up,up 04/09/98))
OBSERVING PROCEDURE
You might have to offset the telescope to get the
object to where the observers want it on the (windowed) CCD.
Example: Offsets in RA +25arcs and +60 in DEC to get the
object near the centre of a 300x300 window with xstart=365, ystart=556 (TEK2).
Although you can enter an aperture offset to take this into account, it's probably
better to offset 'by hand', as the actual telescope position is needed for finding
guidestars in GSS.
Once on the object, you'll stay very long as a typical
3D cube consist of 55x60sec exposures.
*** Remember to remove the agmirror (AGMIRROR OUT) before starting the
exposure ***
DATA HANDLING
Observing logs:
Because no script has been developed yet to extract all the necessary TAURUS
header information, you will need to create two logs per night: One for the
archive (normal nightlog, from lplogs account), and one special TAURUS log
for the observer. Better yet, this log has to be done
by hand!.
A template log (taurus.log) is stored in the logdata directory.
(A special TAURUS account also exists on lpss1). AT the end of the night, print
the log using a2ps -1 -nd -F6 -nL -l <logfile> | lpr -Pwht_laser and store it
together with the normal nightlog in the observinglogs folder.