ARCoIRIS Observing Guide

This page gives basic information on TripleSpec4 observing strategies.  The information covered in this document is:
(1) Detector Orientation on the Sky
(2) Daytime Calibrations
(3) Telescope Zero-Point
(4) Telescope Focus
(5) Object Acquisition
(6) Taking Spectra

Detector and Slit Orientation:

The slit for TripleSpec4 is aligned along the rows of the imaging detector.  The orientation of the detector on the sky depends upon the Cassegrain rotator.  The Rotator Angle is not the same as the Instrument Position Angle.  In many cases the observer will want to observe the object of interest at a specific instrument position angle such as the parallactic angle for a stellar object or along the major axis for an extended object.  Please note that the acceptable range of rotator angles for TripleSpec4 excludes the range from 88-92 degrees due to a physical limit of the rotator mechanism  

TripleSpec4 is mounted at the Cassegrain focus of the Blanco 4-m telescope.  When the Rotator Angle is 0 degrees, the Instrument Position Angle is 90 degrees (North Up and East Left).

Daytime Calibrations:

(1) Make sure that all dome lights are off.

(2) TripleSpec4 starts with both detectors off.  Turn on the detectors by clicking the red "Detectors Off" button in the Spectrograph Detector window.

(3) Select the Observation Type to be "Dflat" in the Spectrograph Detector window.

(4) Turn off the SV detector by clicking the SV On button

(5) Make sure that the calibration system mirror, M4, is in the "Park" position.

(6) Ask the telescope operator set the dome flat lamp intensity to 150 units.

(7) Take dome flats with an exposure time of 2 seconds by pressing the "Start" button.

(8) Turn the dome flat lamps off, i.e., lamp intensity 0 units

(9) Take dome flats with the lamps off and an exposure time of 2 seconds by pressing the "Start" button.

(10) Ask the telescope operator to place the calibration system mirror, M4, in the "Lamps" position.

(11) Select the Observation Type to be "Calibration" and select the "Hollow Cathode" lamp.  The hollow cathod lamp is a CuHeAr that shows He and Ar lines.

(12) Take five 2-second arc lamp exposures with the lamp on and five 2-second exposures with the lamp off.  This will be done automatically by clicking on the "Start" button in the Spectrograph Detector window. 

Telescope Zero-Point

(1) Ask the telescope operator to move to a "bright" star near zenith.

If the telescope pointing is good, the star should appear in the 4' by 4' FOV in the "Image Detector" window.  

(2) You can then move the star to the region of the imaging detector where you would like to zero-point with offset tool.

(3) The star will now be centered in the field.

Telescope Focus

(1) Move the telescope to a field.    This can be one of your science fields or your zero-point field.  Make sure that the guiding is turned off.

(2) Select the "Focus Wide" script in the Spectrograph Detector window

(3) Ask the telescope operator for the appropriate best focus value that is calculated from the TCS.  This value will be the middle value of the focus sequence.  Enter the value in the "args" box next to the script menu.

(4) Execute the script by pressing the "exec" button in the Spectrograph Detector window.

(5) The focus_wide script will now run.  It takes seven images of the field at different focus values.  The focus value previously entered will be center value.

(6) When the script is completed, run the "ts4focus" task in the IRAF window.  Select stars by marking them with the "m" key and hit "q" to quit.

(7) The "ts4focus" task will then plot a curve of FWHM of the measured star(s) versus focus.

(8) You should see a parabola with the best focus noted.  If not you can display the images in IRAF and examine them with the "imexam" task.

Object Acquisition

In progress.

Taking Spectra

In progress.