HET documentation:

    Our documentation pages continue to evolve and improve, and a number of old/deprecated pages have been removed. This updated "Observing Status" page remains the central location for information about sky quality, observing statistics, and more:  https://hydra.as.utexas.edu/?a=help&h=7   In particular it provides links to access the daily "Night Report", the "OPS Report" (which includes the list of high priority targets highlighted for that night's observations), daily VIRUS bias exposure snapshots, and much more! Take a look and let us know if you have questions or requests for more content.

HET Acknowledgements and citations:

    The HET Board of Directors recently approved an updated policy for how to cite acknowledge HET observations and instruments in your publications. Please see here for the full details: https://hydra.as.utexas.edu/?a=help&h=61

New LRS2 finder image code:

     There is a new code that generates a cut-out image from PanSTARRS and overlays the LRS2 IFU footprint at the correct orientation (example image below). The code is available here: https://github.com/sjanowiecki/HET_lrs2_finder    This is intended to help users understand and interpret their LRS2 observations, particularly in crowded or complex fields with multiple sources in the IFU.

Collecting Efficiency

    We are working towards implementing a significant improvement to the Phase II Target Submission Language parameterization of sky transparency. Instead of requesting N/S/P conditions (0%/50%/90% transparency), users will soon request a minimum value of Collecting Efficiency (CE) for their observation, where:

    Collecting Efficiency  =  Sky Transparency * Primary Mirror Pupil Illumination

This will give users more detailed information and control over their data quality. There is documentation available to describe how to estimate CE for your targets and what types of values are reasonable to request: https://hydra.as.utexas.edu/?a=help&h=140
    Sky Transparency varies between 0 (cloudy) and 1 (clear) and Pupil Illumination varies between 0.5 (tracker at extreme edge) and 1 (tracker centered over the mirror), so CE varies from 0 to 1. Note that we also provide an online Filling Factor Calculator to determine the maximum pupil illumination available for a given declination and exposure time. Experienced users will be aware that longer exposures experience worse pupil illumination: at Dec=+45deg, a 10min exposure has an average pupil of 97% but a 30min exposure has only 91% pupil illumination. This impact should be considered carefully when requesting CE in the future!
    Beginning in 23-1, Users will have access to the CE for each of their observations through the "Objects Observed" tab in their program interface on Hydra. Please use this opportunity to become familiar with the typical values of CE during regular observations:

Remember that "Sky conditions" (green arrows above) include the average sky surface brightness (in the listed SDSS filter) during your exposure, and the average transparency in parentheses. The new column for C.E. appears under the orange arrow in the screenshot above.
    Starting in 23-3 we hope to transition to CE and discontinue the use of SKYTRANS. Additional information will be forthcoming about this important transition.

MOONDOWN TSL keyword

    Starting in the 23-2 trimester (1-April 2023) we will introduce the new TSL keyword "MOONDOWN" which can be used to request that the moon be below the horizon during the entire visit (and that the visit be completed within the dark portion of the night between 18-deg twilights). In the past, SKYBRIGHT_X (where X = g, r, or i) of exactly 21.0 was an indication that the moon should be below the horizon. Starting in 23-2 we will treat the sky surface brightness keyword literally and offer MOONDOWN as an option for users who wish to request that.

HPF wavelength drift

    As many users have already noticed, the HPF spectrograph is experiencing a larger-than-normal wavelength drift after the summer 2022 engineering maintenance. The LFC calibrations are able to fully correct for this drift, and the HPF team is investigating possible causes. The drift appears to be slowly stabilizing and should not cause an impact to science users.




The "November 2023 Jump" is discussed further in Suvrath's "Note to HPF Users" included in the 22-3 End of Trimester report.