STDSOP is a tool to prepare quickly OBs for observations of telluric strandard, needed for night time SofI spectroscopical calibrations. In addition to the speed, the tool somewhat reduces the danged for making mistakes, because the instrument set ups are well defined.

To start the tool, type at the prompt in the SofI workstation (sofi@wsofi): stdsopMain &

Using the tool requires some planning: the user needs to decide before if the telluric will be observed before or after the science target. The tool input parameters are:

1- Target coordinates;

2- Approximate LST at the middle of the target observation; this mean the middle of taking the spectra, not the middle of the science OB execution, because a long acquisition may lead to 10-15 min difference between these, and for a rising or a setting target this can easily translate into more than 0.2 difference in sec z; if the target was observed first, just check in the fits file headers with Gasgano (or IRAF, or MIDAS, or IDL) what was the the LST in the middle of the science sequence.

3- The LST when you expect to be in the middle of the standard's spectroscopic sequence; typically, the acquisition of a bright standard requires about 10 minutes, and the actual spectroscopic sequence that consists of one A-B pair takes at most 5 minutes.

4- Instrument set up, including: mode (low resolution blue or red, or high resolution H or K grisms), and slit width; the tool automatically creates an OB with the desired slit in the first template after the acquisition, AND a slit of 2.0 arcsec in the second template after the acquisition, that is intended for spectrophotometric observations when the user wants to use the standard also for flux calibration - if this is not the case, just skip the second template in BoB.

5- Maximum airmass difference between the target and the telluric; the typically adopted limit is 0.2 in sec z, but it is recommended to reduce the difference to 0.1 or better; this is not always possible, especially in the parts of the sky away from the plane of the Milky Way; you may have to select a telluric among fainter stars or to widen the spectral type range (iw. from B3 - B4 to B1 - B9).

6- Magnitude range of the telluric stars - refer to the SofI User Manual for the recommended numbers.

7- Select from a list (available via pull-down menu) the catalog from which you want to select a telluric standard; the two most commonly used strategies are to select a B star (typically, for late type target stars or extragalactic science targets) or a solar analog (typically for early type target stars) - refer the the SofI User Manual for a detailed discussion; note that catalogs of non-emission B stars are also available, but they have been cleaned only from the known emission line stars, and there is always a chance that an unknown Be star may lurk out there; therefore, it is important to check the data on the RTD, to make sure that the selected telluric is free from emission lines because emission lines in the standard can make it impossible to reduce the data!.

Once the input parameters are typed in the respective GUI, the user has a stellar catalog, he/she should choose a telluric star from the list, shown in the window bellow (by clicking on the corresponding line). For convenience the list can be sorted by various parameters via clicking on the tabs above each column. If possible, select start close to the target in airmass, AND in RA, i.e. in the same general part of the sky, because the sky transparency changes not just with the airmass, but with the direction.

The visitors may want to write down which telluric was chosen because later the selection disappears from the window (but don't panic if you haven't done it - this information will be written in the fits file header and can be retrieved via Gasgano).

Finally, press "Generate OB". The OB will be generated, and a window will appear, telling what is its name. Note that the telluric standard OBs are written in the SofI workstation, the visitor has no access to them, and they are overwritten every time a new telluric standard OB is generated.

To carry out the observations, the operator will load the OB with BOB, and will run it (Note: these are tasks executed by the TIO, not by the visitor).