During the night, selection of targets to be observed depends on
current conditions, especially seeing, sky transparency, sky brightness
(Moon phase) and distance to the Moon. Night observing schedules will be
adjusted accordingly, if weather changes. For each individual target they
are set in the Phase 2, but the strictest ones must be well defined already
in the Proposal.
In their proposals, the PIs should explicitly give the following information:
- the maximum value of seeing, at which observation may
be performed, in arcsec.
- Air mass
- the maximum air mass/zenithal distance (or minimum
elevation) at which a target may be observed. The recommended value, set by default,
is (30 over the horizon), but PIs may request a lower limit, between
-). Note, however, that the
Atmospheric Dispersion Corrector will not work properly at .
Note also that constraining airmass 2 in the proposal is not allowed.
- Sky transparency
- the sky clearness and magnitude drop due to
clouds, defined as a number between 0 (totally cloudy) and 1 (clear).
- Moon phase/sky brightness
- : the acceptable brightness of the sky,
coming from the illumination and elevation of the Moon - “dark”, “gray”
or “dark+gray”. “Dark” is always 0-3 days from the new moon. Between 4-11 days, “gray” time is defined when the Moon is over the horizon.
HSC runs are not allocated during bright time.
- Moon distance
- the minimum separation from the Moon, at which
the target can be observed, in degrees. Only distances larger than 30 deg are
allowed (to avoid significant contamination with stray light). For “dark” time,
30 deg is set by default, and cannot be changed by the PI. For “gray” time, it
is the PI who sets the constraint.
- Time constraints
- window of time when the PI wants the observations
to be performed. There are no particular limits for its length, and multiple windows
are allowed. It is allowed to put several targets per window, or define several
windows for one object. Note that the chance for the OBs to
be observed becomes higher by specifying the time windows as relaxed as possible.
Note, that if a highly-ranked proposal is intended for restrictive conditions
(for example seeing ) that are not currently met (),
this proposal will not be executed at such moment, and a lower-ranked one that
allows for given conditions () will be chosen. Relaxing the constraints
increases the probability of having observations done.
Defining different constraints for different targets is allowed.
In order to help to choose the optimum observing constraints for your
project, that will increase the probability of execution and still
allow for the science you intend to make, please familiarize yourself with
the Statistical Information for Observing Condition Constraints in:
Since the semester S17A, time-critical observations may be
proposed. If the PI requires the targets to be observed in a specific time,
please provide sufficient information, such as: date(s), time, and duration of
the time windows. Use the Box 13 of the Application Form, or add comments in the
target list (see Sec. 2.2). Note that the chance for the OBs to be
executed may increase by specifying the time windows as relaxed as possible.
If during the proposed time window the environmental conditions (seeing, transparency,
etc.) are not met, the observations will not be carried out.