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Thomas Diehl, 12/18/2012 08:10 PM

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h1. SV StandardStar
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To supplement the standard star fields that are setting at morning twilight, I've created json files for all the DES standard star "E region" fields:  E1-A, E2-A, E3-A, E4-A, E5-A, E6-A, E8-A, and E9-A (E2-A and E4-A should just be duplicates of the previous E2-A and E4-A json files).  I have placed them in the ~DECamObserver/ExposureScripts directory on observer2.ctio.noao.edu, as well as attaching them to the current message. (The file names follow the
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format:  stdstarField_<name>.json.)
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Their coordinates have been adjusted to center them in the N4 CCD:
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    Field     RA(2000)   DEC(2000)
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    -----     --------   ---------
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    E1-A      01:24:50   -44:33:40
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    E2-A      04:03:00   -44:41:45
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    E3-A      06:42:54   -45:05:06
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    E4-A      09:23:44   -45:21:02
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    E5-A      12:04:11   -45:24:03
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    E6-A      14:45:33   -45:15:34
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    E8-A      20:07:22   -44:37:01
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    E9-A      22:45:37   -44:22:47
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I did some checks, and it looks like standard star fields E2-A, E4-A, E5-A, and E6-A -- in combination with the MaxVis and Stripe 82 standard star fields
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-- should provide adequate standard star field coverage through February 14 (although we *might* want to supplement with another field or two for February).
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Some suggestions for taking standard star field observations for the rest of the DES season (through mid-February):
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1. For this first year of DES, it is very important to try to observe
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    at least one Stripe 82 standard star field under clear conditions each
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    night (and preferably the more Stripe 82 fields the better).  Currently,
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    these are the only DES standard star fields with calibrated standard stars
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    covering all the CCDs over the full DECam focal plane.  Since the Stripe 82
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    fields are getting hard to observe in the morning twilight, this means
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    trying to hit at least one Stripe 82 field in the evening twilight.  If
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    sky conditions are not clear during evening twilight, one should try to
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    observe a Stripe 82 field under clear conditions in the middle of night,
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    before they all set too far into the West.
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2. If no Stripe 82 fields can be observed during a clear period during the
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    night, the MaxVis standard star field is a less-preferred-but-still-adequate
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    second choice.
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3. For some nights, due to clouds, #1 and #2 above will be impossible to achieve.
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    Data taken on these nights will have to be photometrically calibrated at a
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    later stage of the DESDM pipeline -- so, not a disaster, but a situation
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    that we prefer to avoid if possible, since it causes more work on the
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    data processing side of things.
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4. To check which standard star fields are in a good position to observe
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    (airmass < 2.10 and moon separation > 15 deg), use the decamStdFieldsTimeDate.py
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    on observer2.ctio.noao.edu:
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    source ~/dtucker/bin/setup_StdStarFieldPicker.csh    (or .bash if you are using bash shell)
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    decamStdFieldsTimeDate.py --help
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    decamStdFieldsTimeDate.py --UT='2012/12/19 00:43'
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5. It is usually better to observe your high-airmass standard star field
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    first, since generally its airmass will be changing the fastest.
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Many thanks for your help, and best wishes for good observing!