Basics

We need four kinds of calibration data for this run.

  • biases (in the afternoon)
  • twilight flat fields (both evening and morning twilights): in filters U, Us, B, V in the blue; and in filters r, R, I, and Y in the red. Note that for the next run, we might have a different filter needs.
  • photometric standards, in well-studied Landolt fields (some are also Stone astrometric fields). The goal is to establish extinctions and color terms on photometric nights
  • spectrophotometric standards, for a few subdwarfs and white dwarf standards. These are used to calibrate the Us and Y bands that are not well calibrated yet, especially Y band. We will only need to take probably twice for this propose.

All OBs are under AZ account, OBs/Calibration

Landolt Fields

We choose four Landold SA fields.

  • SA 95 (RA=3h53, Dec=00:13), OB name is SA95_UsUBVrRIY.ob
  • SA 98 (RA=6h52, Dec=-00:19), OB name is SA98_UsUBVrRIY.ob
  • SA 101 (RA=9h56, Dec=-00:19), OB name is SA101_UsUBVrRIY.ob
  • SA 104 (RA=12h42, Dec=-00:25), OB name is SA104_UsUBVrRIY.ob
  • SA 107 (RA=15h39, Dec=-00:15), OB name is SA107_UsUBVrRIY.ob
  • SA 110 (RA=18h42, Dec=+00:05)

Each one will take about 10 min to execute. These are single exposures in each filter.

Spectrophotometric Standards

We choose four of them:

  • GD50: 0348-0058, this is a WD standard with good WD model, spectrophotometry and is one the fundamental UKIRT standards that are used to set the zeropoints for UKIDSS Z and Y bands. OB name is GD50_UsY.ob

  • G191b2b: 0505+5249, this is a WD standard with good ground-based and HST spectrophotometry as well as good WD model for synthetic photometry. OB name is G191b2b_UsY.ob.

  • GD153: 1257+2201, this is a WD standard with good WD model, spectrophotometry and is one the fundamental UKIRT standards that are used to set the zeropoints for UKIDSS Z and Y bands, it is also one of the four HST fundamental photometric standards. OB name is GD153_UsY.ob

  • BD +26 2606: 1409+2542, this is THE fundamental Oke-Gunn standard that defined the AB mag system. It is bright, so we will use the shortest recommended exposure time (0.3s). OB name is BD+26_UsY.ob.

Each OB will take about 5 min.

Afternoon Bias

Each night starts with a series of 25 biases and three darks. After a few test biases using Biastest.ob , take 25Bias3Darks.ob .

Evening Twilight Flat

In the evening twilight, one can usually do four sets of OBs, in this order, a UY OB, a U_sI OB, a BR OB, and a Vr OB, with PA=0. Each is a set of five with dithers.

Start with test OBs to estimate exposure time. Then: Skyflat_UY_5.ob, Skyflat_UsI_5.ob, Skyflat_BR_5.ob, Skyflat_Vr_5.ob

Evening Standards

As soon as twilight flats are done, for the first two photometric nights, do the spectrophotometric standards:

GD50_UsY.ob and G191b2b_UsY.ob

For any photometric night, execute a set of three SA fields: SA95_UsUBVrRIY.ob SA98_UsUBVrRIY.ob SA101_UsUBVrRIY.ob , NB, SA101 is probably too low (airmass >2.5) at the beginning of the night.

Midnight Standards

For any photometric night, execute a set of three SA fields: SA98_UsUBVrRIY.ob SA101_UsUBVrRIY.ob SA104_UsUBVrRIY.ob

Morning Standards

For any photometric night, execute a set of three SA fields: SA101_UsUBVrRIY.ob SA104_UsUBVrRIY.ob SA107_UsUBVrRIY.ob

And finally, for the first two photometric nights, try spectrophotometric standards: GD153_UsY.ob and BD+26_UsY.ob .

Morning Twilight

We will do PA=180 set. Skyflat_Vr_180_5.ob , Skyflat_BR_180_5.ob , Skyflat_UsI_180_5.ob and Skyflat_UY_180_5.ob. And then go to get some sleep.

-- XiaohuiFan - 06 Feb 2008
Topic revision: r3 - 26 May 2008, XiaohuiFan
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