Astrophysics

Data acquisition and storage

PMIS software under WINDOWS 98 is used to control the CCD and for data acquisition. Data from the PC are transfered by ftp to the SUN (Ultra1) computer for image analysis and storage. The SUN is equiped with a DAT drive (/dev/rmt/0n). A CD-writer on the data acquisition PC can also be used for data storage. 4-mm DATA tape and read & write CDROMS are usually available at the observatory. Click here for instruccions for writing data on the DAT and CDROM.

 Quick user's guide to PMIS 

 

• Start-up

To start PMIS, click on the PMIS logo on the acquisition PC. Before clicking, make sure that the PC time/date is the Universal Time/Date. You may use the following formula to set the PC clock:
UT = Sonora Time + 7hr (both winter and summer).
PMIS command window appears with a prompt "Cli>".

PMIS is a menu driven acquisition software. Data acquisition can be done either in the command mode or using the menu options. You can choose CCD parameters such as CCDformat, binning, gain etc by following the Menu or giving the appropriate commands on the command window. Values set in one mode are available for all the subsequent images, irrespective of whether command line or menu option is used

 

• Data Acquisition using Menu

Open an image window by clicking on Image on the command window. To take images go to Acquire and then click on expose (and select intergration time), or bias for object or bias exposures. Once the exposure is over, you need to save the image using File followed by Export and FITS 16. You have the option to give a comment to be included in the header by clicking on File followed by Image Info before saving the image. The image header will not include none of the observational parameters.

 

• Data Acquisition using Macros

In this mode, images are taken by typing the commands on the PMIS command window. Each command is driven by a macro. We have a growing set of macros to overcome the limitations (e.g. overscan, fits headers, multiple image acquisition) of menu driven data acquisition system. We recommend that you use these macros. The instructions for their use are as follows:

Cli> imdir "directory" "[Observer]" "[S]"

----------------------------- Set-up observational parameters
The command imdir sets the directory (e.g. "C:\usuarios\ydm\n1") in to which images will be written. The directory should have already been created. Optionally, the observer's name also can be entered, which will go directly into the header of all the files created in the session. In the default mode ("S" as the third parameter), a CCD format of 1124x560 with the origin at X=0 and Y=232, suitable for the B&C session is chosen. To open a session for direct imaging you should choose "I" as the third parameter. This opens an image window of 1124x1024 pixels. Note that both the CCD formats include 100 pixel overscan. The sessions are opened with default values of gain (value of 4) and no binning. If you wish to change these values, follow the "Acquire" and "Acquisition Area" on the image window menu. A logfile named "log.txt" is created in the image directory. Information such as exposure time, UT are directly written into this text file. The command also initializes the counter number of multiple observations of bias, HeAr lamp and images to 0. Root names for multiple bias and HeAr observations are defined as "bias" and "hear" respectively. These default parameters may be changed by redefining them on the command line as shown in the following examples:

Cli> vdef biasnum 1
Cli> vdef hearnum 1
Cli> vdef objnum 1
Cli> vdef biasfil "n1bias"
Cli> vdef hearfil "n1hear"
Cli> vdef objfil  "n1obj"

 

IMPORTANT: Please make sure that all the image and graphic windows are closed (i.e. only the command window should be open) before running "imdir". Also note that both the command line parameters should be written inside double quotes. Quantities enclosed inside square brackets such as [comment] are optional parameters. Cli> obj "file" t "[comment]" "[filter]"

 

---------------------------------- Take 1 exposure of t secs

Obtains an exposure of "t" secs and stores the data in a FITS file called file.fit. If a filter name is given as the 4th parameter, it will be written into the FILTER header. There is protection against overwriting and hence if the file already exists or if the file name contains more than 8 characters, the program exits and you need to start with a new filename.

Cli> nobj "file" t n n0 "[comment]" "[filter]"

 

---------------------------------- Take n exposures of t secs each
Obtains n exposures of "t" secs each and stores the data in FITS files. Filenames are formed as fileXX.fit, where XX=n0,n0+ 1,....,n0+ n-1. If any of the files already exists or if the file name contains more than 6 characters, the program exits and you need to start with a new filename. Maximum value of n=99.

Cli> ndark "file" t n n0 "[comment]"

 

---------------------------------- Take n exposures of t secs each
Obtains n dark exposures of "t" secs each and stores the data in FITS files. Filenames are formed as fileXX.fit, where XX=n0,n0+ 1,....,n0+ n-1. If any of the files already exists or if the file name contains more than 6 characters, the program exits and you need to start with a new filename. Maximum value of n=99.

Cli> mltbias n "[comment]"

 

---------------------------------- Take n biases
Obtains "n" bias frames and stores them in the disk. Names are of the form biasfilXX.fit [n1bias1.fit, n1bias2.fit etc], where XX is an incremental number initialized by imdir or later set using vdef.

Cli> mlthear t n "[comment]"

 

--------------------- Take n HeAr arc spectra, each of duration t secs.
Obtains n exposures of t secs each and stores the images in FITS format files named hearfilXX.fit [n1hear1.fit, n1hear2.fit etc], where XX is an incremental number initialized by imdir or later set using vdef.

Cli> mltobs "file" t n "[comment]"

 

--------------------- Take n object spectra, each of duration t secs.
Obtains n exposures of t secs each and stores the images in FITS format files named fileXX.fit [n1file1.fit, n1file2.fit etc], where XX is an incremental number initialized by imdir or later set using vdef.

Cli> note "comment"

 

------------------------------ Write comment lines to "log.txt"

About the macros: The macros are relatively new and hence may not be bug-free. Macros imdir, mltbias, mlthear and mltobs were the first macros and were developed by Alejandro Terlevich during (April 2000, October 2000) (text of the original macro release). Macros obj, nobj and ndark are improved variations of these macros and are developed by D. Mayya. All these macros write the data in FITS format files. Header KEYWORDS EXPTIME, DATE-OBS, DATA-TYP, UT-START, CGAINPAR, XBINNING, YBINNING, DISPAXIS, TELESCOP, OBSERVER, INSTRUME, FILTER and COMMENT are written into all the FITS files. The macros obj and nobj have protection against overwriting of files.

 

IMPORTANT: When defining "imdir" make sure that the directory is empty or else you will risk erasing files such as bias0.fit, hear0.fit when using mltbias and mlthear. For some reason you want to continue writing data on an old directory, you can redefine the numbers using vdef command.

 

Data storage

Data from the PC are transfered by ftp to the SUN (Ultra1) computer for image analysis and storage. The SUN is equiped with a DAT drive (/dev/rmt/0n). A CD-writer on the data acquisition PC can also be used for data storage. 4-mm DATA tape and read & write CDROMS are usually available at the observatory.

 

TIPS

Use "Acquire" on the image window menu to take test images.

You can use "obj" or "nobj" to take HeAr arc spectrum (instead of mlthear).

Use "nobj" to take multiple flat-field exposures.

Macros create .FIT images, but IRAF tasks do not recognize .FIT as a fits file. Hence use the unix command "mv" or the iraf command "rfits" on the sun to convert file name extension .FIT to .fits