Operating the telescope

The status window/display

The upper section of the status window gives information about the telescope/dome systems. The left column gives the current RA, DEC, hour angle of the telescope, coordinate epoch, and position angle. The next column gives the azimuth, altitude, rotator, focus positions for each of the three focus motors, and tertiary port. The rightmost column gives the current UT, local sidereal time, airmass, and the focus position in a coordinate system which gives mean focus, xtilt, and ytilt.

Other entries give the dome position and status (initialized/unitialized, slaved/not slaved, open/closed), and mirror cover status (open/closed).

If any of the items appear in reverse video, there is likely to be something configured such that you will have significant problems with your observations (e.g., the dome is closed!). Note that no mirror covers are currently installed, so the status of these can be ignored.

The telescope positions are not absolutely encoded, so the status only reports where the computer thinks the item is, which is not necessarily where it really is, although if things are working well, the computer should correctly know where things are. However, if something seems peculiar, it is important to check with the remote video cameras and/or by going out and looking at the telescope/dome!

If you hit a key in the status window, it will toggle into engineering mode, where some additional information is displayed, and where a graphical window will come up which shows a running plot of the current encoder positions relative to the desired positions. If you accidentally do this, you can minimize the plot window, and switch back to normal mode by hitting a key again in the status window.

The command window

All commands should be entered in the command window. For all commands, you will not get a command prompt until the previous command completes.

The software allows you to write simple scripts in an external file which can be read in by the program to issue a series of commands automatically. Input script files should have commands which are identical to what you would need to type in the command window. To execute a script, you use the command:

INPUT filename

where filename is the name of the file with the commands to execute. Our convention is to use .inp as the extension for script files. A script can call another script, up to 5 layers deep.

Restarting tcomm

If for some reason things appear to hang up (i.e., nothing returns for several minutes after you'd really expect it to, you can restart the tcomm programs after issuing a CTRL-$\setminus$ in the command window. This should kill all of the windows, and then retyping tcomm should start everything up again. However, if this is necessary, please inform Jon of the circumstances - we would really like to get things working without ANY hangups.

Dome commands

Telescope commands

Moving the telescope

The following commands can be used to move the telescope:

User catalogs

Users can create catalogs of object positions which can be referenced by an ID number to maximize efficiency and minimize input error during the night. The format of the user catalogs is identical to that used by REMARK on the 3.5m. Each object should be put on a separate line with the following format:

object name $<$TAB$>$ RA (hh:mm:ss) $<$TAB$>$ DEC (dd:mm:ss) $<$TAB$>$ epoch $<$TAB$>$ (proper motion in RA) $<$TAB$>$(proper motion in DEC)

The following commands can then be used with these files:

Coordinate epoch and update commands

The default coordinate epoch on startup in 1950. The default epoch for coordinate entry can be changed using:

Focus commands

The telescope can be focussed by moving the position of the secondary. The secondary position is controlled by three separate motors, so the mirror can be tilted as well as pistoned. Tilting the mirrors changes the collimation and thus is not a motion which should normally be done! All focus positions are negative: (0,0,0) is when the secondary is at the home position, farthest from the primary.

Note that the focus is a function of temperature, since the telescope structure expands/contracts as a function of temperature. As the temperature increases, the focus decreases, i.e. goes more negative.

The focus commands are:

Camera programs

All camera commands are normally entered in the command window, but these are passed to the appropriate camera control program, which are usually run from separate windows on the right part of the desktop.

After images are taken, they are normally written out to disk in FITS format. The images go into directory images/yymmdd under the tcomm home directory, where yymmdd refers to the current UT date. The default filenames are yymmdd.index.fits where index is a running index number: both the root filename and the index number can be changed, see below.

The image display window

The first time an image is taken, each camera program opens an Image Display window on the console; each subsequent image will be displayed in this window. Once an image has been displayed, some interactive commands are available in the display window, provided that a wait for input or any other I/O is not pending. To interact with the image, simply move the mouse onto the display window. The current pixel location of the cursor will be displayed in a frame at the base of the image display along with the pixel intensity. The arrow keys are used for fine control (one pixel at a time) of the cursor position. Note that, to maintain a small window, the image as originally displayed will likely only show every other, or even every 4th pixel (depending on the detector)

The following mouse buttons and keyboard keys are active while the mouse is located on the image display:

Mouse Buttons
Button Function
LEFT ZOOM IN, centered on the cursor
MIDDLE ZOOM OUT, centered on the cursor
RIGHT PAN, move the pixel under the cursor to the center

Keyboard Commands
Key Function
R RESTORE image to the original zoom/pan
+ BLINK Forwards through the last 4 images.
- BLINK Backwards through the last 4 images.
P Find the PEAK pixel near the cursor & jump the cursor there
V Find the LOWEST pixel ("Valley") near the cursor & jump the cursor there
# "Power Zoom" zoom at the cursor to the maximum zoom factor
H Toggle between small and full-screen cross-hairs
] Clear boxes and stuff off the image display

Color Bar Adjustment:

If you place the mouse on the color bar, these commands are available to adjust the contrast of the image:

Hold down the LEFT Mouse button, drag the left end of the color bar.

Hold down the RIGHT Mouse button, drag the right end of the color bar.

Hold the MIDDLE Mouse button, "roll" the color bar left or right.
The position of the mouse cursor displays the range of intensities represented by that color.

Pressing the R key while the mouse is on the color bar restores the original color map (undoing any change of the contrast or "roll" changes made with the mouse buttons).

Note that you can also redisplay the current image with a different stretch using the SCALE command, see below.

Camera Commands

The following commands are available:

Standard star observations

Several commands are available to increase your efficiency in observing standard stars. There is a full catalog of all of the Landolt standards, plus several others, in the top level observe directory, with filename standards.apo. To allow use of this catalog in conjuction with your own catalog of objects, there are separate commands to open and read from the standards file, so you can have both the standards file and a user file open simultaneously. The standards file also includes the UBVRI magnitudes of the stars, and the observing program knows about the throughput of the 1m telescope, so the program is also capable of choosing reasonable exposure times for you.

The relevant commands are:

Guiding commands

The current guider CCD is a camera purchased from Finger Lakes Instrumentation; it uses a E2V 1024$\times$1024 CCD with 13.5$\mu$ pixels.

In general, you can issue the same commands to the guider CCD as you can to the science CCD. To do so, use the same command names but preceeded by the letter ``G'', e.g., GEXP t will take a guider exposure of length t seconds.

Since our telescope is a three-axis telescope (alt-az-rot) and a single guide star only contains two positions (x-y), the absolute quality of the guiding depends on an accurate pointing model (although less so than if there were no guider at all!). We use the guider observations to update altitude and azimuth, and assume that the rotator angle is correct. Since the guider is located off axis, errors in the rotator angle will manifest themselves as small arcs of stars in the science camera, centered around the position of the guide camera (which is off of the chip).

To start guiding, first take a guider exposure to see if there is an acceptable guide star and to determine a good exposure time. Ideally, you will have a star which has good S/N with an exposure time of less than or approximately equal to 1 second. Once you have a picture taken with a good exposure time, you can start guiding by issuing the GUIDE command. This will take a picture with your exposure time, ask you to mark the guide star in the guide CCD image, and will then start autoguiding on this star.

If your original image was taken in full frame mode (WINDOW FULL), then all guiding images will be done with a small subframe around the guide star. If your original image was taken in windowed mode, then all guiding images will be taken with the same windowing.

Guiding will continue until you do a slew with the telescope or unless you issue a GUIDEOFF command.

Other commands relevant to guiding: