The tcpcom guide

ALFOSC Fast Photometry Control Program Startup

• Log in to the computer sandra as obs1 (password provided by staff).
• In a command line window, type fastphot_start to start the script that will set up the proper environment and run tcpcom in a separate window.
• The tcpcom program presents the instrument/system status across several pages. Use the number keys on the number row (not the keypad), to change page. Page 0 contains the most vital information for normal operation. Page 2 contains detailed status on the instrument filter/aperture/grism wheels. Page 3 contains the status on the FASU filter wheels. Each page presents a short menu with the most important keystroke commands for the relevant page. Some commands can only be accessed from that particular page, while the more common commands can be accessed from any page. Page 8 and 9 provides some help.

Important points to get started:

• After the tcpcom command interface window has appeared, go to page 2 to check that the filter wheel is coming to the right position, and especially that the grism and aperture wheels are out of the way (they must be in the open position = position 8). If they are not, use the G-key and the I-key to get the grism and slit out of the way. The FASU filters can be accessed from page 3. Check that they also are in the open position. The calibration lamp unit can not be accessed from tcpcom. If somebody left the mirror in the last time ALFOSC were used, you must quit the tcpcom program and start ALFOSC again to turn it off, before restarting.
• For on-line help, refer to page 8 and 9.

Data files

• Full (or reduced x/y size) frames are by default saved with a similar naming convention to the BIAS program (for example "ka010001.fits"). The name base (the first four letters) can be changed as desired.
• Windowed frames are the key to the fast photometry mode. These files contain a stream of pixels according to the window list prepared by the user, in the order the pixels are read out from the CCD (see the setup procedure below). These files are named "w00000.fits", with numbers increasing from the first frame obtained. It is possible to change the names in tcpcom, but that will imply that this name must be passed on to the processing software rtp, when it is started. These frames cannot be viewed with saoimage, unless they are converted with the rtcnv program first.

Output data directory

• The master data directory is /data/data1/ for obs1.
• The subdirectory for each night is created with names following the naming convention from the standard ALFOSC interface, BIAS, (i.e. ka01 is Jan 1 2001).
• The user must create subdirectories below this directory for each photometry run (using the `D'-key).

Filters and such

• The filter is changed by hitting the `f'-key.
• The current list of filters is then displayed. The list can also be viewed by going to page 2 and pressing the `P'-key.
• The aperture (`I'-key) and grism (`G'-key) can be changed only from page 2.
• The FASU filters (`U' and `V') can be changed only from page 3.
• It is possible to install extra filters in the grism wheel if more than 7 filter are required, and use the G-key to set that particular filter, in combination with the open position in the filter wheel.
• The positions of the filter, grism and slit wheels are all saved to the FITS headers, as well as the FASU filter positions.
• It is possible to change filters during readout to save time. Use the number keys [1-8] for this, not the normal f-key. Note that there will be no signal that an action has been taken until the readout is complete.
• After a change of instrument filters and update of the setup files, the `R'-key (in page 2 or 3) will read these files and the menus are updated.

Normal CCD imaging

• `T' sets the exposure time and `e' starts an integration with the current time. `E' sets the exposure time and immediately starts the integration.
• `d' starts a dark integration, that is; integration without opening the shutter and `b' starts a bias integration.
• The `a'-key can be used to abort an integration. It can also be used during readout, in which case you will be prompted for confirmation, and any other keys than `y' will continue the readout.

Setting up for fast photometry

1. Obtain an image of your target field
   • Move the telescope to the target field and start autoguiding.
   • Create a new directory for this specific photometry run by using the `D'-key in the tcpcom window. The directory may exist, but note that old files in this directory will be overwritten.
   • Update the FITS comment and object fields, if you care.
   • In normal full-frame imaging mode, get a picture of the field. (The `E'-key sets exposure time and starts the integration.) Wait about 80 seconds for the readout to complete.
   • Use saoimage to check that the field is good. You may want to move the field to get enough good reference stars within the field. Notice the defects on the CCD, and check that your target and reference stars are not on any obvious defects. Keep moving the telescope and taking images of the field until you are certain that you have a good position. You never move the telescope once you are in place.
   
   
2. Mark your target objects for windowing
   • In the directory where the image of the field was stored, give the command phot < filename >, where < filename > is the name of the image of the field that the telescope currently points to.
   • You should get a saoimage display that (after a while) will show the image of your field, scaled close to the background value to reveal all details.
   • Mark your target, reference stars and sky fields. The order is important, so mark the target first, then all reference stars you want, and finally one or more sky background fields. The key to use is `s' when the image cursor is at the desired position. When done hit `W' to write the window coordinate lists. The file photwins.dat will contain the list of windows in the order they were selected. Channel #1 will be the first entry, and so on. The other file, photwccd.dat, contains the list sorted in the CCD readout direction. This list must be sent to the camera controller to initialise the windowed readout. These two lists are vital to reconstruct the photometry windows when processing the data, so take care that they are not accidentally deleted.
   • The marked windows may not always appear as such, unless the image is scaled 1:1. You can check that the box markers are really there by moving the pointer to the field and watching the magnifier window in the upper right corner of the saoimage display.
   • The interactive saoimage display is slow. Be patient when the marker shows a bell. The cursor will jog back and forth between the terminal where you started saoimage and the saoimage display when the screen is updated. This is just saoimage doing its things. Try not to get confused.
   • See the phot guide for more info on the photometry window setup program.
   
   
3. Start photometric imaging
   • First transmit the window list to the controller by hitting the `w'-key in the tcpcom window. Note that the "TRANSFER MODE" field in the top right corner switches from "FULL FRAME" to "PARTIAL FRAME". (Use the `t'-key to toggle it back to "FULL FRAME" when the fast photometry run is complete.)
   • Set a sequence time interval (`S'-key).
   • Hit the `i'-key. This will do a readout test to measure exactly how long time the current window setup will take to read out. After a few seconds the result is reported and the exposure time is set to the highest value possible with the given sequence time interval.
   • Start the sequence with the `s' key. Give the desired number of frames, or 9999 to run for ever (or until the sequence is aborted with the `a' key).
   
   

How to exit the tcpcom program.