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Observation Preparation

, Updated

This section mainly describes how to prepare and check MAROON-X observations. 

Phase II observations should be set up using the Template Observations included in your program. These will be filled in with the targets and observing conditions from the Phase I proposal. It is recommended to start with these template observations in the OT and follow the How to Prepare your program note.  See also the MAROON-X OT Details below for more detailed instructions.

MAROON-X OT details:

The OT does NOT have a special instrument component for MAROON-X. However, there is little to configure as MAROON-X has only one mode. Please fill out the Visitor Instrument section of each Observation. Add spectro-photometric, telluric, and RV standards as normal target observations but make a note if the telluric standard(s) need to be swapped against a similar target closer in airmass to the science target. How to include additional calibrations (e.g., bracketing etalon frames) is tbd.

Name: The Visitor Instrument name should be set to "MAROON-X" 

Exposure Time: The exposure time field should be filled in with the desired integration time for each target. In the current OT version,  "Exp Time" is the sum of the actual exposure time and 100s readout time. The example shown in the figure above represents exposures of 500s with 100s readouts.

Position Angle: The "Pos Angle" field sets the position angle of the instrument on the sky (degrees East of North). The default should be 0.0. In this case the telescope de-rotator will be taken out and the parallactic angle will be kept stable instead of the field angle. If a fixed field angle is indeed desired please specify this in the notes.

Wavelength: The "Wavelength" field is used by the TCS to calculate the relative atmospheric dispersion with respect to the guide wavelength, and should be set midway of the wavelength coverage of MAROON-X, hence ~0.7um;

Notes on guiding:

MAROON-X is using the PWFS2. Please first specify the obeserving conditions and it will allow OT find a guide star automatically. If this fails the "Auto" guide star group will be empty, in which case you should use the "Manual GS" button to search for another which will not vignette the science target. Since the FOV of MAROON-X is small the guide probe arm can be moved closer to the field center than for other instruments. We recommend a 30” clearance to the field center so that the sky fiber located 20” off-axis remains fully unvignetted. Please email your Contact Scientist if you have any questions.


Acquisition overheads associated with setting up on each new target include time for slewing the telescope, configuring, and starting the PWFS2 guiding, and centering the target on the fiber. These sum to ~10 minutes. Acquisition overhead of 10min per observation is automatically accounted for in the OT.

Because MAROON-X has its own active guiding and flexure compensation, re-acquisitions are not required.

The readout time for each pair of frames (blue and red arm) is 100s (dominated by the longer readout time of the red detector).

Switching between science and calibration observations or different calibration sources should be budgeted with 30s.