Preparing Observing Scripts

Observing with DECam is quite simple, straightforward and very efficient. Every exposure sequence will perform every step in the process automatically, from moving the telescope and dome, setting up the filter, focusing, finding suitable guiding stars and start the guiding, taking the exposure, building the images and finally, storing of the data. The preparation of observing scripts will make a night with DECam efficient, and hence, more relaxed.

For preparing the scripts there is a convenient, stand-alone software (python based) which can be downloaded and installed in any computer. The tarball of the ScriptsEditor software and full documentation can be downloaded as tarballs from the following links:

• Python 2 version
• Python 3 version (Recommended!)
• Documentation (also available in the tarballs above)

Are you sharing your nights with other projects? Read This about Prop-ID!

ScriptsEditor is also available at the computers in the control room (observer2) in case that modification or creation of scripts during the night is needed.

Depending on your python distribution, you may need to install the modules TKinter, json and pyephem to make ScriptsEditor work on your computer.

ScriptEditor allows to easily plan observations with different dithering patterns or centering objects on a particular CCD, among other features.

The DECam observing system expects scripts to be written in .json format (a text file with special formatting). ScriptsEditor takes care of that. However, some people feel more comfortable working on simple text scripts. Scripts in .txt format are possible but they will need to be loaded anyway to the ScriptsEditor and saved in .json format. A .txt script is made of a set of exposures, each exposure in a single line, with the observing parameters separated by a comma.

This is an example of a .txt script which makes sets of 3x60s exposures in bands g, r and i, with no dithering:

ExpType = object, ra= 281.0, dec=-29.866, filter = g, expTime = 60, object = Sgr, count = 3

ExpType = object, ra= 281.0, dec=-29.866, filter = r, expTime = 60, object = Sgr, count = 3

ExpType = object, ra= 281.0, dec=-29.866, filter = i, expTime = 60, object = Sgr, count = 3

The same script will look this way in .json format:

[
{
"count": 3,
"expType": "object",
"object": "Sgr",
"filter": "g",
"RA": 281.0,
"dec": -29.866,
"expTime": 60
},
{
"count": 3,
"expType": "object",
"object": "Sgr",
"filter": "r",
"RA": 281.0,
"dec": -29.866,
"expTime": 60
},
{
"count": 3,
"expType": "object",
"object": "Sgr",
"filter": "i",
"RA": 281.0,
"dec": -29.866,
"expTime": 60
}
]

The possible parameters for defining an exposure are the following:

Parameters related with the Exposures

Parameters related with the Input Coordinates

Parameters related with Sequences

You can specify the requested telescope position in a number of different systems: ra and dec, ha and dec, az and el. You can also specify an offset relative to the current telescope pointing using the deltaRA and deltaDEC keywords. In most cases both sexagesimal and float degrees formats are supported. If you do not specify coordinates in your exposure request the image will be take at the current telescope position.

Additional explanations on the exposure parameters can be found in the ScriptsEditor documentation included in the tarball.

Special tools to prepare observing scripts for standard stars are described here.

Notice that the community pipeline will automatically ignore images with any of these words in the title (i.e. in the parameter object): junk, pointing, focus and donut. These images will still be stored at the NOIRLab Astro Data Archive but they won't be processed. More details here.

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The propid keyword

Image headers will contain your Prop-ID (your project number, for example 2016A-0343) under keyword "propid". It is very important to setup the right propid since the access to your data through the NOIRLab Astro Data Archive depends on it. During proprietary time only you and your collaborators will have access to the data taken under your Prop-id.

In normal circumstances (observing only one project in a night) the exposures will take the Prop-ID from the setup information entered every afternoon. However, it has become more and more common to share time with other projects. In those cases, it is convenient to incorporate the keyword "propid" in your observing scripts. Unfortunately, this is something that the ScriptsEditor software is not currently handling, and thus it must be incorporated by hand or using your own script. The extra keywords have to be incorporated as strings, for example:

"propid" : "2016A-9999",

"proposer" : "Smith",

"program" : "The title of my program"