Spanish Service Time


Current Service Proposals at INT, TNG, NOT.


Observing nights are offered to the CAT astrophysical community as part of Spain’s allocated observing time (CAT) on the INT, NOT, and TNG. A “Reactive Time” is available to the CAT on the Liverpool Telescope (LT) — conditions may change from semester to semester, see below. Service Time is also available at the WHT, although proposals must be submitted directly through the ING Service Program. The service nights at the WHT are shared by proposals from different nationalities. For all the telescopes, service-time proposals are scientifically reviewed by the CAT (the Principal Investigator will receive the report of the appraisal). Observing priorities are fixed by the scientific merit of the proposals.

Service proposals can be submitted at any time, although a strict limit of 10 days before any observing date will be applicable to those proposals requesting a particular service night. Service observations requested to visitor-mode telescopes (INT, NOT, and TNG) will be performed by IAC support astronomers. Service observations on the WHT and LT will be performed by ING and LT personnel, respectively. See the RECOMMENDATIONS made by the IAC team of support astronomers at the end of this page.


  • Service observations on the INT, NOT, and TNG must follow all rules explained in the standard “call for proposals” of the corresponding semester. This includes revision of protected targets and observations available in the Observatories archives.
  • Service observations on the INT, NOT, and TNG must not exceed four hours of observing time per night. As for the WHT, see the list of rules (in principle, up to 8 h can be requested). Service proposals will be ranked on the basis of scientific value and technical feasibility. Successful proposals will be added to the observing list typically within two weeks from submission. Programs will remain in the list up to 12 months, or until completion. Every service night, the list of proposals in the observing queue will be checked to identify suitable targets, and these will be prioritized according to their ranking and instrument availability.
  • The TNG has a policy of protected targets. Please read carefully and respect the approved rules.
  • LT Reactive Time: up to a maximum of 9.5 h for the CAT in semester 2022A (1 Jan – 31 Aug 2022).
  • LT Reactive Time is offered in a “Reactive Time” mode with the intention to provide rapid access to LT observations. A summary of the rules of use is provided next:
    • Proposals should typically limit their request to 3 h or less and must be led by a researcher of a Spanish institution.
    • This mode is suitable for targets of opportunity and test observations that may be helpful for the preparation of longer programs. Other categories are also accepted but must be well justified.
    • All proposals will receive a scientific appraisal by the CAT as soon as possible after receipt. If accepted, the requested observations will enter the telescope queue according their scientific ranking and urgency.
    • Proposals can be submitted at any time during the current semester.
    • Applicants should check the complete list of rules.
    • Applications must be sent using the web-based form prepared by the LT staff. In the TAG flag, applicants must indicate “CAT”.
  • Publications deriving from service night data should include suitable acknowledgement of the origin of any images arising therefrom and identification of the tasks carried out by the support astronomers group.

For further information on the CAT service time on the INT, NOT and TNG, send an email to: ttnn_a [at] iac [dot] es. For further information on the LT Reactive Time channel, send an email to catiac [at] iac dot es.


Recommendations made by the support astronomers team

The less restrictive a proposal is in terms of seeing and atmospheric transparency more likely it is to be carried out. This is especially critical in the INT telescope, where is not unusual to have a seeing less than 1″5 in U band, or less than 0″8 in I band. For IAC80 and TCS, the seeing is usually more than 1″ in any photometric band.

Although the scientific case for one proposal may have a high punctuation, for some telescopes/instruments it is not possible to carry out programs which require many filters or grisms. This is particularly relevant for the INT in both, its wide-field camera (with only 6 holes in its filter wheel) and its IDS spectrograph (where only one diffraction grating can be mounted). In these cases, it is not advisable to request for many different configurations for the one observing night, but it is desirable to give as many different setting options as possible to achieve the scientific goal.

Proposals requesting observations at certain given times during one night are possible, if they are splitted into two or more sets and the total time does not exceed four hours. However, in practice, this condition may enter in conflict with other programs, which implementation would be constrained by the temporal windows open by these proposals. Therefore, having the same punctuation, proposals with temporal restrictions could be less successful.

We recommend to provide realistic time requests in your proposals and to take always special care with overhead times. Some instruments, like NOTCAM at NOT, have overhead times which exceed 50% of the total required exposure time. Use always the specific tools offered by the different websites of each instrument to estimate realistically the corresponding overheads. Proposals which do not determine precisely integration times and overheads cannot be completed.

The support astronomers, the ones carrying out these observations, cannot know all the details of your observational project that are not described in your proposal. It is the IP’s responsibility to get familiar with the required instrumentation and to describe all the required procedures (dithering, offsets, reading modes, etc). The symbols used in the finding chards should always be specified, as well as their sizes on the sky, orientation, bands, etc. The SA group do not carry out or double check any calculation. However, we are at your disposal to answer questions and to provide guidance on the process of preparing your proposal. Please, contact the “support astronomers” group at ttnn_a [at]