This log is based on the latest information from archived images only.
The purpose of this automatic log is to report the number and type of
photometric standards observing groups observed during a given run by
MegaCam. With only two "Q97" OGs per night (one at dusk, and one at dawn,
when sky conditions allow), observing runs of about 14 nights, and five
filters to cover, this strategy gives at least three iterations per filter
per run. A diversity in the fields observed is welcome, hence a mix
of OGs taken at dusk and dawn for a given filter is welcome. This is
made easier to keep track of with the color code adopted here for the
font: purple stands for dusk, while green stands for dawn.
Information of the various fields can be found on
this page.
Of prime importance is the first of the four QSO flags (e.g. "P 1 V Q"): the
value of the flag can be either "P" for Photometric or "A" for Absorbed. It might
happen that when the Sun rises, observers would notice that SkyProbe did not
catch super thin homogeneous cirrus, leading them to think the night was photometric.
In such case, the exposures get assigned the "A"bsorded flag and should be
dismissed in accounting how many sequences are acquired per run for each
filter.
Note that since the primary and secondary standards (short exposures) are defocused
by 0.5mm (Smith et al. standards in the Landolt fields) or 1.5mm (bright HST standards),
Elixir reports a bogus image quality measurement based only on cosmic rays (usually
less than 0.5 arcsec.). The 2 minute exposure on the CFHTLS Deep field (tertiary standards)
is however normally focused and should report an image quality consistent with the night
performance.
