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Cal-G10 » History » Version 2

Gary Bernstein, 08/28/2012 10:38 AM

1 1 Douglas Tucker
h1. Cal-G10
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3 1 Douglas Tucker
_"It is known whether 1st-year photometric accuracy will be enhanced by targeting standards fields in the middle of nights in addition to evening/morning twilight standards. "_
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5 1 Douglas Tucker
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h2. Prerequisites
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8 2 Gary Bernstein
* Zeropoints and extinction coefficients calculated for all standards-field exposures during SV
9 2 Gary Bernstein
* RASICAM data in hand.
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11 1 Douglas Tucker
h2. Procedure
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13 2 Gary Bernstein
* Compare middle-of-night zeropoints and extinctions coefficients to mean of morning/evening twilights.
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* Calculate RMS deviation of midnight to twilight zeropoints, evaluate statistical significance.
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* For cases where midnight standards differ from the twilights signfiicantly: what conditions indicated by RASICAM?
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* Use night of hourly standards to determine whether midnight standards improved ability to interpolate proper zeropoint to hourly standards.
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h2. Verdict
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* If there is no detectable difference between midnight and twilight photometric solutions, except in cases where RASICAM indicates non-photometric conditions, then midnight standards are superfluous.
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* If midnight standards differ from twilights, but hourly variations are seen to be equally large, then midnight standards are superfluous since they cannot track the night's photometric variations anyway.
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h2. Consequences
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* Absence of photometric variation between twilights means that DES observations need to explicit nighttime standards.
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* Fast photometric variations will have impact on ubercal algorithms' assumptions.
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* Useful midnight standards should be incorporated into OBSTAC algorithm, that some field with standards gets observed near middle of photometric nights.