TCS and Autoguider: Basic Procedures
Presetting the Telescope
Entering object coordinates
It is possible to enter object coordinates in two ways: directly in the TCS panel, or through a catalog.
To enter coordinates directly on the TCS panel, click on the input line located on the Presetting portion of the TCS control panel, delete any previous coordinates and enter the coordinates of the object, RA first and declination last, leaving a space between RA and DEC and no spaces within each one (HHMMSS -DDMMSS). Click on the input line on the right, labeled Epoch and enter the coordinate's epoch.
If you prefer you can make a catalog with different objects so you don't have to enter the coordinates every time you change objects.
To do so, open a text editor in the TCS workstation and write the coordinates of the objects, one per line with the following format:
Name HHMMSS.ss -DDMMSS.ss Epoch Prop.Mo.RA Prop.Mo.DEC
The sign in front of the declination is optional if it is positive. The decimal numbers are also optional, including that of the epoch. The epoch is mandatory, otherwise it will default to 00.00. The proper motion values will default to 0.0 also if you don't enter them.
Once you have entered the desired objects in the text file, save it as /home/tcs/catal/name.cat replacing name with a suitable name.
Go to the TCS Control panel and press Cat.Select on the Catalogue Handling portion of the panel. It will show a window with the different catalogs stored on the directory. Click on your catalog and click on OK. Now the catalog should be loaded in the Catalog Handling portion of the panel. Use the UP and Dwn buttons to highlight the desired object. Once chosen, the object coordinates should be entered automatically in the input fields above.
Once the coordinates of an object has been entered in the coordinates input fields, press the Preset button. The Telescope Status field should show PrstToObj. Wait until the word Guide show up on the same field; it indicates that the telescope has arrived at the desired coordinates. If the telescope doesn't move after you have pressed Preset then it is possible that your object is out of the telescope's safety zone; check the Messages window for an error message.
Acquiring a Guidestar
Once you have positioned the telescope on the desired coordinates you will want to pick a guidestar. To do so follow this procedure.
- Press the Retrieve Field on the AG Field Acquisition portion of the TCS Control Panel.
- Wait until the acquisition image has loaded on the Real Time Display, on the right hand monitor of the TCS workstation and the word Complete appears on the CCD Stat field, on the Autoguider portion of the TCS Control Panel. It is very important to wait for the image to load completely before doing anything else, otherwise you risk crashing Fiera, whose restart procedure could take twenty minutes or more.
- If the acquisition image doesn't begin to load on the RTD after a reasonable amount of time (1 minute aprox), go to the AG Process workspace, kill every window there, open an xterminal and type the command /home/tcs/m2p2/bin/agWSStart.sh. Wait for the four text windows to appear and repeat the process. If the four text windows do not appear it is very possible that Fiera has crashed. Try to take a science test image; if it doesn't work go to the procedure to restart Fiera in the Notes for Observers document located in the control room.
- Once the acquisition image is completely loaded the RTD, click on the Pick Object button on the Pick Reference Star panel on the right hand monitor. If the panel isn't there, open the TCS menu on the RTD panel, click on Pick Reference Star and wait for the panel to appear. Click on a suitable guidestar. A box should appear centered on the star. Click on the Star To Box button on the Autoguider portion of the TCS Control Panel. After a little while a small window should appear on the RTD with the selected star centered on it. The images of the guidestar should be refreshed continuesly and the AG Stat field on the Autoguider portion of the TCS Control Panel should say ACTIVE. Also the Telescope Status field on the TCS Control Panel should say Offset and Ofsinpr alternatively as the autoguider starts to correct the position of the star. If all these conditions are met, the autoguider is active and you can start your science exposure. Otherwise, turn off the autoguider clicking the Off button and try to start it again with the Star to Box button. If that doesn't work, try pressing the OFFSET button, on the Virtual Handset on the TCS Control Panel before starting the autoguider again.
- Sometimes it happens that images of the guidestar stops arriving to the autoguider. If you see the autoguider window frozen that is the case. Go to the AG Processes and repeat the process of killing and restarting the text windows there, as described above. If that doesn't work, Fiera could have crashed. Test with a short science exposure and restart Fiera if necessary.
- After Restarting the text windows on the AG Processes workspace, or after restarting Fiera, the autoguider will lose the position of the guidestar and the acquisition process should be started from the begining.
Performing a Combined Offset
A combined offset is the action of moving the telescope and the autoguider window a small amount, so the autoguider can keep track of the guidestar and the time consuming procedure of acquiring a guidestar can be avoided for small offsets.
To perform a combined offset follow this procedure:
- Turn off the autoguider, clicking on the button Off on the Autoguider portion of the TCS Control Panel.
- Check (if it is not already checked) the button Combined Offset on the Virtual Handset portion of the TCS Control Panel.
- Enter the amounts of the desired offsets in RA and Dec on the input fields below the Virtual Handset and press the Apply button to load the values into the software. This input fields only accepts positive numbers; the direction of the offsets is given by the button of the handset you press.
- Press the apropiate buttons on the virtual handset to perform the offset and wait for the word Offset on the Telescope Status field.
- Press the Star to Box button on the Autoguider to switch on the autoguider again.
IMPORTANT: Always turn off the autoguider before performing a combined offset; otherwise you risk crashing Fiera and the procedure to restart it can take more than twenty minutes.
The autoguider shares the same filter frame with the science mosaic, so, when you change filter the guidestar won't be exactly in the same place than with the previous filter due the differences in refraction coefficient of the different filters. You must turn off the autoguider before changing filters, wait for the new filter to be in place, and restart the autoguider with the button Box to Star. This way the telescope won't jump to recenter the guidestar when you start the autoguider.