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Time Refund Policy

Refunds for technical problems, not user mistakes

Time is deducted from a science program’s allocation when an observation is attempted, not when an observation is successfully completed. LCO will refund the time deducted for an observation (to the nearest 0.1 hour) if the author of the request (or the PI on the science program) reports that some or all of the data acquired during the observation are unusable, and the reason for their unusability is a technical problem arising from LCO’s hardware or software. Requests for refunds must be submitted to LCO’s Science Support Team: Requests for refunds must include the observation’s Request number or Request Group number. If a refund is granted, the time for the unusable data is credited to the proposal’s total allocation.

LCO does not refund time for an observation if the reason that the data are unusable is a mistake made by the request’s author. Selecting inappropriate configuration parameters (e.g. filters, exposure times) qualifies as a mistake. Members of LCO’s staff are available to provide advice on observing strategies and to review draft observation requests. Users seeking assistance composing observation requests should contact Please keep in mind that LCO cannot provide immediate feedback. Requests for assistance should be submitted as far in advance of the observing window as possible.

Because LCO does not (yet!) schedule observations based on atmospheric transparency or seeing criteria, we also do not refund time for observations made in less-than-optimal conditions. If images/spectra are unusable because of clouds, refer to the "Observations through clouds" section below. If images/spectra are unusable because a telescope was severely out-of-focus (i.e. a focus-mechanism failure, not bad seeing), then we will refund the time.

LCO users whose requests for refunds are denied may appeal the decision to the LCO Director (

Proposals are allocated hours strictly per semester. LCO does not allow unused hours to be “carried over” from one semester to the next. Therefore, refunds must also be requested before the end of a semester.

Observations through clouds

The trickiest refund requests for the Science Support team to adjudicate are those submitted for observations that are obscured by clouds. Since the start of routine operations (2014), LCO’s robotically-operated sites cease observing and shut the enclosures when the atmospheric transparency drops below 25%. The transparency is calculated from a measurement of the sky’s temperature in the 8-14 µm range, made by one or more cloud sensors. The sensors are pointed roughly 10° away from zenith, and they have an approximately 80° field-of-view. The cloud sensors are calibrated several times per year. The transparency criterion for open/close decisions generally works because most observations are made with the telescopes pointed within 50° of the zenith, where the cloud sensors are most sensitive.

Request for refunds for cloud-obscured data generally fall into three categories:

  1. The telescopes were pointed within 50° of the zenith. The site never closed. In this case, we generally decide in the requester’s favor and refund the time. Our justification is that the data are obscured either (i) because the cloud sensors require recalibration, or (ii) because cloud density was insufficient to decrease the transparency below 25%. The former is a “technical problem”; the latter is not.
  2. The telescopes were pointed within 50° of the zenith. The site closed during or after the observations. In this case, the refund request is generally denied. Our justification is that the weather system eventually made the right decision (to cease observations). The fact that the decision wasn’t made sooner is an “honest” limitation of the cloud detection apparatus. (A human observer could have scanned the horizon and seen clouds approaching; the cloud sensors cannot.)
  3. The telescopes were pointed further than 50° from the zenith. In this case, we check the quality of the data from other telescopes at the site. If the other telescopes were pointed closer to the zenith, and the images were obscured, then we assume Case 1 (above) and refund the time. If the other telescopes were pointed closer to the zenith, and the images were not obscured, then we do not refund the time. Our justification is that the sky was clear closer to the zenith, and closing the site for the sake of the obscured lower altitude telescopes would have prevented the acquisition of good data from the other (higher altitude) telescopes.

Beginning in 2023, LCO is switching the responsibility for cloud detection from the cloud sensors to all-sky cameras, which are installed at all sites. The all-sky images show exactly where clouds are and (by comparing observed v expected stellar brightnesses) how opaque the clouds are. In 2021, we demonstrated that we can use the all-sky images to create cloud maps. The ultimate goal of the all-sky camera project is to feed the positions and extents of clouds back to the scheduler, so that it knows what parts of the sky are actually available for science observations.