Dark Energy Survey » DES Operations

h1. Standard Star Instructions

* Standard star fields are to be observed every evening and morning twilight that appear to be clear,

  where "clear" is determined by a quick visual inspection of the RASICAM image, of the TASCA image, 

  or (!) of the sky itself.

* If possible, for each twilight period, 3 standard star fields should be observed:  one at low airmass 

  (X<1.25), on at medium airmass (X=1.25-1.65), and one at high airmass (X=1.65-2.10).  It is generally 

  better to observe the high-airmass field first, since its airmass will be changing the most rapidly.

* For half-nights, 1 or 2 fields -- preferably a low-airmass field and a high-airmass field -- should 

  be observed just before switchover.  (If only one field, a high-airmass field is preferred.)

* For evening twilight, use the *DES/standard/Yzirg* scripts (which start with Y-band and end with g-band);

  for morning twilight or pre-switchover, use the *DES/standard/grizY* scripts (which start with g-band and 

  end with Y-band).   (For those rare nights when we also observe in u-band, please use the corresponding 

  "DES/standard/Yzirgu" and "DES/standard/ugrizY" scripts.)

* There are several useful scripts in the StdStarPicker package in the DECamObserver account on observer2,

  including decamStdFieldsTimeDate.py and decamStdFieldsQueryNextSet.py.

* *To check which standard star fields are in a good position to observe (airmass < 2.10, moon separation 

  > 15 deg, within Blanco horizon limits), use decamStdFieldsTimeDate.py:*

<pre><code>

  source ~/dtucker/bin/setup_StdStarFieldPicker.csh      (or .bash if you are using bash shell)

  decamStdFieldsTimeDate.py --help                       (for detailed help)

  decamStdFieldsTimeDate.py --UT=now                     (for a list accessible right now)

  decamStdFieldsTimeDate.py --UT='2013/09/17 00:43'      (for a list accessible at 00:43UT on Sept 17, 2013)

</code></pre>

* *To get a preferred triad of standard fields -- a low-airmass field, a medium-airmass field, and a

  high-airmass field -- for a given time and date, use decamStdFieldsQueryNextSet.py:*

<pre><code>

  source ~/dtucker/bin/setup_StdStarFieldPicker.csh      (or .bash if you are using bash shell)

  decamStdFieldsQueryNextSet.py --help                   (for detailed help)

  decamStdFieldsQueryNextSet.py --UT=now                 (for a triad accessible right now)

  decamStdFieldsQueryNextSet.py --UT='2013/09/17 00:43'  (for a triad accessible at 00:43UT on Sept 17, 2013)

  (Warning: decamStdFieldsQueryNextSet.py will output a default json file, "stdstar.json".  Just ignore it.)

</code></pre>

* *For simplicity, a look-up table of preferred triads for the nights of August 30-Sepember 30, 2013, 

  listing the preferred triad for each 15-min interval throughout those nights, can be found here: 

  attachment:listOfStdsByUT.Sept2013.txt*

h2. The Standard Fields

*SDSS Equatorial Fields:  "Golden Standards"*

|_. Field Name  |_.  RA    | _.Dec     |

|SDSSJ0000-0000 | 00:00:00 | +00:00:00 |

|SDSSJ0100-0000 | 01:00:00 | +00:00:00 |

|SDSSJ0200-0000 | 02:00:00 | +00:00:00 |

|SDSSJ0320-0000 | 03:20:00 | +00:00:00 |

|SDSSJ0843-0000 | 08:43:00 | +00:00:00 |

|SDSSJ0933-0005 | 09:33:00 | -00:05:00 |

|SDSSJ0958-0010 | 09:58:00 | -00:10:00 |

|SDSSJ1048-0000 | 10:48:00 | +00:00:00 |

|SDSSJ1227-0000 | 12:27:00 | +00:00:00 |

|SDSSJ1442-0005 | 14:42:00 | -00:05:00 |

|SDSSJ2140-0000 | 21:40:00 | +00:00:00 |

|SDSSJ2300-0000 | 23:00:00 | +00:00:00 |

*HST CalSpec/Other Fields: "Silver Standards"*

|_. Field Name  |_. RA     |_. Dec     |

|C26202/HST     | 03:32:30 | -27:46:05 |

|MaxVis         | 06:30:00 | -58:45:00 |

*Graham E-Region Fields (Southern u'g'r'i'z' fields): "Bronze Standards"*

|_. Field Name  |_. RA     |_. Dec     |

|E1-A           | 01:24:50 | -44:33:40 |

|E2-A           | 04:03:00 | -44:41:45 |

|E3-A           | 06:42:54 | -45:05:06 |

|E4-A           | 09:23:44 | -45:21:02 |

|E5-A           | 12:04:11 | -45:24:03 |

|E6-A           | 14:45:33 | -45:15:34 |

|E8-A           | 20:07:22 | -44:37:01 |

|E9-A           | 22:45:37 | -44:22:47 |