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Planning ObservationsBefore applying to use INGRID you need to carefully plan your observations, particularly if you want to use INGRID with AO correction. The information that you need to put in your proposal includes:
This section is divided into two sections, concerning observations with and without AO correction.
Guide Star Requirements for AO CorrectionWhen using INGRID with AO correction, a suitable guide star is required for every science target. These guide stars should satisfy the following requirements. Note that if the science target itself satisfies them, then it can be used as the guide star.
No AO Correction - Do I need a Guide Star?When using INGRID without AO correction, you must establish whether or not you need a guide star for telescope guiding. If your individual integrations will be short (~ a few minutes) then you can simply use the telescope tracking to observe your science target. In this instance no guide star is required. (Note that there is ~1" drift in tracking over a ten minute timescale.)
For longer integrations you will need a guide star, however the requirements are much less stringent than for performing AO corrections. Note that if the science target itself satisfies these requirements, then it can be used as the guide star.
If you are using INGRID with
AO correction you should consider whether you need to use PSF
calibration stars. An AO-corrected point spread function (PSF)
typically comprises of a near-Gaussian diffraction-limited core with a
faint 'blobby' pattern extending over a disk of similar radius to the
uncorrected seeing. If, for example, you are looking for faint close
companions to another object you will want to know whether what appears
to a companion really is one, or whether it is simply a PSF
If you do decide to perform PSF calibrations, you must select target
(a) If the science target is being used as the guide star, you
should locate a star within a few degrees of the target that is of
comparable magnitude (generally to within ~0.2 mag, although this can
be relaxed for V<10).
(b) Calibrating the PSF when the science target is different from the guide star is non-trivial in the sense that it varies strongly with both radius and position angle from the guide star. (The major axis usually points towards the guide star.) The most trivial solution is to look at the PSF of stars close to the science target - unfortunately the density of stars in the field is rarely high enough for this. A better approach is to search for separate star pairs satisfying these properties:
To search for suitable PSF stars you can use either this PSF star finder or this PSF star-pair finder.
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