The `tcpcom` guide

ALFOSC Fast Photometry Control Program Startup

Log in to the computer tessa as obs (password provided by staff).
In a command line window, type fastphot_start (tech: Which should be a link to ~fastphot/bin/fastphot_devel3) to start the script that will start up the tcpcom program 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 or any lamps on the last time ALFOSC were used, you must quit the tcpcom program and start ALFOSC again to turn them off and/or take out the calibration mirror, before restarting.
Check on Page 2 that the ALFOSC internal focus is set to the correct value, which is (10/5 2006) '1653'. (Or use the ALFOSC UIF to do it).
For on-line help, refer to page 8 and 9.

Data files

The tcpcom program produces two types of output 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 directly with DS9. Use rtcnv to convert them into a FITS files.
Note: there MIGHT be an offset in pixel values when cutting out the windows. If you use full frame flatfields and the photwins.dat file tells you to cut out at x=100,y=100 according to the observed offset you should actually cut out at x=102,y=99. (Note that this is not well investigated and has been reported by only one observer so far.)

Output data directory

All data files is stored in subdirectories below a top level data directory decided for the current date when tcpcom is started.

The master data directory is /fastphot-data, that is owned by user obs.
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 tcpcom program can control all wheels in the ALFOSC instrument, as well as the FASU filter wheels.

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

The tcpcom program is capable of doing basic CCD imaging, although this option is intended only to get quick images of the current field to set up the fast photometry target list. You will not be able to see the image during readout, but will have to load it into DS9 once it is completely written. The readout program reports the median of the pixel counts as it reads out, which is very useful when doing flat fields. Basic tcpcom keystroke commands for imaging is shown on the menu for screen 0.

`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

To start fast photometry on a target it is necessary to follow a very precise procedure that goes in three steps.

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 DS9 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.
Mark your target objects for windowing
- Load a full frame, unbinned image into DS9.
- Press 'Region' In the DS9 function bar.
- Click on the target object to mark it.
- Click on comparison objects to mark them.
- Finally, click on sky regions to mark them. It is important that the sky regions get marked last.
- Click on 'Region->Save Regions...' and accept the default name ('ds9.reg').
- Run the command photcnv in the same data directory where the 'ds9.reg' file is.
- The default window size is 64x64 pixels. If a different window size is desired, specify this by giving the option -s size to photcnv.
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. Be aware that tcpcom will actually not display anything different. The only way to see that it has been done is to watch the "Time since last CCD clear" number. When it starts from zero again the function has been completed.
- 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).

Now you should leave the tcpcom window alone until you want to abort the sequence. Frames will be retrieved and stored automatically. While tcpcom stores the window frames, you may process the results with the Real Time Photometry program, to get light curves of your targets.

How to exit the `tcpcom` program.

Before you exit tcpcom, make sure to put the transfer mode back to 'full frame transfer mode', using keystroke 't'. If you forget this, the standard ALFOSC CCD control program BIAS will hang once you make an exposure.

An alternative solution is to reset the CCD controller (staff only).

Known problems:

Sometimes a sequence file is skipped due to a harware error in the camera controller. When this happens, the observer should copy the sequence file before(i.e. w00012.fits) to the missing name (i.e. w00013.fits) and make a note of this in his/hers observing log.

The tcpcom guide