Observing Strategies

MAROON-X has only one fixed instrument setting and currently one readout mode (100kHz, 1x1 binning). Observing strategies depend on the science case, i.e. whether general purpose echelle spectroscopy or high-resolution radial velocity observations are desired. The latter will require more careful planning of calibrations, both instrument stability tracking via the simultaneous calibration fiber as well as bracketing etalon exposures during the night.

Since MAROON-X was designed for high-precision radial velocity measurements, some design compromises are limiting the ability of the instrument to obtain spectra of very faint objects. The MAROON-X internal tip-tilt guiding system works reliably only for targets with a peak SNR of at least 30 within a hypothetical 30min science exposure time. You can check if a proposed target will be bright enough with MAROON-X ETC, by entering the target's magnitude, spectral type, required observing conditions, and a 30min science exposure time.

Exposure time limit: The 100um thick high-rho CCD in the red arm collects more and longer cosmic ray signals than a classical thin epitaxial CCD. The CCD has also a few cosmetic artifacts that have a stronger impact on pixel neighbors based on exposure time. We thus advise to limit individual exposure times to 30 min or less.

Signal limit:  The spectrum is distributed over three fibers, sampled by 10 spatial pixels each (hence 30 pixels per 1D spectral bin). Hence the signal level in each stripe is lower than in the combined spectrum. For long exposure times (and hence high level of cosmic ray hits) this might compromise the ability for outlier rejection if the signal level per pixel is so low that optimal extraction techniques are no longer feasible.

Detailed information about the Gemini Phase I Tool (PIT) can be found here.

Phase I Checklist for MAROON-X Proposals

• Instrument configuration:
  • ​N/A (there is only one mode)
• Telescope peripheral wavefront sensors:
  • PWFS1 and PWFS2 are used for MAROON-X. PWFS2 is the default.
• Calibrations:
  • Are the baseline calibrations sufficient? If not, has sufficient observing time been requested for additional calibrations?
  • ​Is accurate removal of telluric lines needed? If so, have telluric standard stars been included?
  • Are long-term (multi-month) high-precision (<1m/s) radial velocity measurements needed? If so, have suitable RV standard stars been included?
• Observing time:
  • ​Did you confirm the exposure time and S/N using the MAROON-X ITC pages?
  • Did you adjust the observing conditions specified to match your requested conditions?
  • Are overheads included in the time requested in your proposal?
  • Are overheads included for additional calibrations?
  • Does the S/N ratio from the ITC result in the required RV uncertainties for your targets?
• Observing conditions:
  • The throughput of MAROON-X is highly dependent on the effective image quality. Has a realistic IQ and airmass setting been used in the ITC to predict the S/N ratio and thus RV precision?
• Scheduling constratints:
  • MAROON-X observations are scheduled in multiple 1-2 month-long blocks in each semester, covering around 75% of available nights. During those blocks, MAROON-X participates in regular queue observing.
  • In the Scheduling section of the PIT, in addition to the timing constraints, please also specify the minimum number of nights requested for the program.
• Target duplication:
  • MAROON-X data are not yet searchable on the Gemini Archive.
  • In the meantime, please check this spreadsheet to see if a particular target has been observed previously or is scheduled to be observed with MAROON-X.
  • You are welcome to email us (maroonx_science@gemini.edu) for specific observing information about targets listed in the spreadsheet (e.g. exposure time, cadence, timings, etc.). You can also request data products for previously-observed MAROON-X targets as long as the proprietary period has elapsed.