Open Use Observations Policy

Rules to follow at the summit

We ask observers to follow the policy below in order to make observations safely at the Mauna Kea summit and to improve the performance of the Subaru telescope.

  1. The Subaru telescope safety rules require that nobody should stay at the summit for more than 14 hours. Telescope operators will start the telescope shut down procedure at 6:30 am accordingly. Please finish all observations by 7 am and leave the summit immediately.
  2. Telescope operators will decide to change the dome rotation direction, to close the main shutter, or to evacuate observers from the summit under strong wind or high humidity weather conditions. Please follow the operators' decision.
  3. Focus checks will be carried out with the autoguider probe at the beginning, middle, and end of observations to confirm the 2ry mirror control system is working correctly and, more importantly, to acquire data to improve seeing. It takes about 10 minutes for each focus check.

Policy for making observations not listed in the proposal

The following policy has been enacted for observers who wish to perform observations not listed in the proposals.


Open use observing time must not be used for observations which were not specified in the proposals, because the telescope time has been allocated for the observing plans with specific targets and observing modes properly evaluated and accepted. There will be cases, however, when open use visitors cannot perform their proposed observations because of unexpected operational or weather requirements. As a result, they may want to use part of their telescope time for observations not listed in the proposals. The Director of the Subaru Telescope would like to respond flexibly in such cases, provided that the modified observations do not conflict with the clearly prohibited cases stated below. We wish the open use observations to be as productive as possible and the telescope time should be used efficiently.

Expected Cases

Case A: More than 1 hour of time is expected
This case may be expected to arise when a support astronomer closely works with visiting astronomers in the preparation of observations. If it occurs, the support astronomer should prompt the visiting astronomers to submit a plan for the extra observations (title and targets) to Michitoshi Yoshida (Director) and Tae-Soo Pyo (Science Operation Division Chief) [,]. The Director will give the final decision.
Case B: Less than 1 hour of time is expected or is suddenly available during observations
If the time is expected in advance, visiting astronomers should follow Case A. In most cases, however, time will often become available unexpectedly during, or at the end of, observations. If it occurs, the support astronomer should check if the extra observations do not conflict with the clearly prohibited cases and should make the final decision. The support astronomer should immediately report the case to the Director (e-mail or verbal).
Case C: When planned observations cannot be done due to bad weather
Visiting astronomers should make observations based upon their backup proposals. The support astronomer should check that the backup observations do not conflict with the clearly prohibited cases, because observing targets are not specified in many of the backup proposals.

Clearly Prohibited Cases

  • Observing the targets listed in other accepted proposals with similar observing modes.
  • Observing the targets listed in guaranteed time observations (GTO) with similar observing modes. GTO targets must be listed in the Call for Proposals.


When visiting astronomers make observations not listed in their proposals, they must describe it in the Open Use Report Form. Subaru telescope will summarize the use of time under such circumstances and will report to the Subaru Advisory Commitee.

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