ABSTRACT
This document is intended to acquaint people with the hardware and software used to make astronomical observations at the Manastash Ridge Observatory (MRO). It includes a basic description of the instrumentation, filters, computers, and software used at MRO and a step-by-step description of commands and procedures needed to observe with the MRO instrumentation. Observers may also turn to the MRO Observer's Check-list for useful information on observing procedures at MRO.
An index to this document
A Description of the instrumentation
The Telescope Control Computer
The Data Acquisition Computer: spinach
Table 2: MRO Broad Band Filters
Table 5: TCC Commands
Logging into LinuxTable 7: Common Linux/Unix CommandsObsparsSettings for using the filter slideUsing the filter translation fileThe autoguider menu optionsThe autoguider guide mode keys
Starting up the guider: a step by step procedure
Table 9: Autoguider OrientationMaking autoguider finding charts
Figure 4: An example finding chart
1 A Description of the instrumentation
The MRO 30-inch is an f/13.5 telescope with a plate scale of approximately 20 arcseconds per millimeter. Mounted approximately 1 inch behind the Cassegrain focus of the telescope are achromatic focal reducing optics that transform the f/13.5 beam into an f/7.0 beam, providing a working plate scale of approximately 38.8 arcseconds per millimeter. The focal reducing optics are optimized for the wavelength range of 3650-8520 Å. The current focal reducing optics were installed in the telescope in 1997. A description of the performance of these optics can be found in the engineering report "New Focal Reducing Optics for MRO!" (but note that this report was done with the old camera!).
An automated filter slide with room for six 2-inch square filters sits between the field and objective lenses of the focal reducer. The filter slide is therefore integral to the current telescope configuration and cannot be easily removed. In addition to its support of the focal reducing optics, the filter slide also contains an inclinometer which may be used for initial alignments of the telescope. The this inclinometer is used when the TCC "Z" command is invoked. The "Z" command is a way to quickly set crude telescope coordinates.
The filter slide is capable of switching filters and of tilting the filters in the beam in order to tilt tune narrow band interference filters. There is a 15 degree range of tilt available with the filter slide. The tilt can be controlled to the nearest 0.05 degrees.
The control of the filter slide is done by means of an embedded controller. This controller communicates to the TCC over a 9600 baud RS-232 link. The embedded controller understands a small set of ASCII commands which are documented in "The MRO Filter Slide". Unless there are problems with the filter slide, the user will not have to know about these low-level commands. The normal way of controlling the filter slide is by setting parameters in "instrpars" and then taking an exposure with the "observe" command. The instrpars settings for the filter slide are documented below. However, there are times when one might wish to move the filter slide without having to take an exposure. The TCC "W" command is provided for this purpose. To use the "W" command you will have to know a few of the low-level commands to the filter slide controller. The most commonly needed commands are documented below in Table 6. Pay particular attention to the filter slide "o" command which will reset the filter slide origin.
The power supply for the filter slide is located above the filter slide on the North side of the telescope. A single toggle switch must be thrown to turn on the filter slide. A green LED on the west side of the filter slide will turn on when the filter slide power is on. The filter slide responds to power by sending the message "Welcome to the MRO filter slide!" to the TCC. If the communications are working properly, this message should be displayed on the TCC monitor directly after turning on the power. No harm is done by turning on the filter slide before the TCC is booted, but in this case the communications check will not be made.
The filter slide remembers its configuration even when it is powered off. Before turning the filter slide power off, it is a good idea to first move the filter slide to filter position one. This moves the filter carriage out of the way of the filter slide cover. In this manner the carriage mechanism and the filters themselves are protected against possible collisions with the filter slide cover when it is being removed and installed. There is a detailed write up on the use of the filter slide in the file "/home/local/text/fslide.doc". Most users will never need to look at this documentation.
In April, 2005, a new imaging system will be installed at MRO to replace the previous "Tbird" imager, whose Cryotiger cooling system failed in late autumn of 2003. The new camera, an Andor Technologies DU-434, features software-controlled thermoelectric cooling and is housed in a hermetically sealed evacuated casing. Like its immediate predecessor, the Andor camera features a thinned, back-illuminated, 1056 x 1027 pixel Marconi CCD. The pixels are 13 µm x 13 µm in size, and when used behind the focal reducing optics the camera has a field of view (FOV) of approximately 9 x 9 arcminutes with each pixel spanning 0.507 arcseconds (1.01 arcseconds in the common 2x2 bin mode). Further details of the camera's performance (including QE, readout noise, and operating temperature range)of the performance will be made available once the installation and testing process is complete.
The Telescope Control Computer (TCC)
The MRO 30" is controlled by a 386-based computer running DOS. This Telescope Control Computer (TCC) contains a multi-module board called a DCX-100 made by Precision MicroControl which handles most of the real-time control of the telescope motors and encoders. The TCC connects to the telescope through a display panel which shows the observer the status of the telescope, dome, and observing floor controls. It connects with the data acquisition computer through a 2400 baud RS-232 link and with the filter slide through an RS-232 link running at 9600 baud. The data acquisition computer communicates with the TCC through a small vocabulary of ASCII commands that are defined in the TCC software. This link allows the data acquisition computer to automatically query the TCC for its current position whenever an image is taken. Up to date position and time information is automatically included in each image file header. Details of the interaction between the TCC and the data acquisition computer can be found in the "Serial Port Command" section of the document entitled The MRO Telescope Control System.
In the telescope control room electronics rack is a GPS receiver which obtains accurate UT time from its satellite links. The GPS clock is linked by a serial cable to a computer (heimdal.mro.cwu.edu) which runs a network time server daemon for the mro subnet. The data acquisition computer updates its system clock by running a network time protocol daemon (xntpd) in the background. In turn, the TCC obtains time updates from the data acquisition computer before each image is taken in an IRAF session. Time labels in the image headers should be accurate to within 1 sec.
There are two hand paddle controls which allow manual control of the telescope, dome, and floor. One hand paddle is located in the control room and the other is out on the observing floor. These manual controls work in parallel. The TCC is capable of moving the telescope position and focus given target values. It can also automatically track the dome position to follow the telescope position. The TCC allows tracking of the telescope in both RA and DEC at rates varying from a few tenths of arcseconds per second to rates in excess of 4 degrees per second. Needless to say, the accuracy of tracking at the high slewing rates have not been verified (nor needed!), but the tracking at stellar and near stellar rates is accurate enough to allow 10 minute exposures without guiding. Details of the software for the TCC are given below.
The data acquisition computer: spinach
The data acquisition system, a computer called spinach.mro.cwu.edu, consists of a 450 MHz Pentium III PC running Linux and the Image Reduction and Analysis Facility (IRAF) developed at the National Optical Astronomy Observatories (NOAO). The data acquisition workstation resides in the control room to the left of the telescope control rack. Within the IRAF environment a user may exercise all of the necessary functions of both of the CCD controllers and the spectrograph. IRAF provides full display and analysis capabilities of images captured by either Tbird or Mustang. Initial display of acquired images is provided by monochrome monitors connected to the CC200 controllers. These monitors are labeled by camera and are located to the left and right of spinach. A mouse connected to Tbird's controller sits next to spinach, the data acquisition computer. This mouse controls an image cursor on Tbird's CC200 monitor and is used primarily to select subregions from an image for focus exposures. This mouse can be used to display pixel values and pixel coordinates on the CC200 screen, but it is recommended that observers avoid use of this mouse for these purposes. Use of the CC200 mouse during image transfers can cause the CC200 controller to hang up.
Connected to spinach is an Exabyte 8mm cartridge tape drive, an internal ZIP drive, and a 10 GB disk drive. The ZIP drive and the Exabyte tape drive are the primary media used to transport data from the observatory to a user's home institution. Although somewhat slow, the Internet connection may also be used for this purpose (best during nighttime hours). Observers should note that each Exabyte tape can hold approximately 2 GB and each ZIP disk holds approximately 100 MB. If data are stored efficiently on the tape, then about 900 unbinned 1024 x 1024 images may be put on a single tape cartridge and a ZIP disk will hold 47 unbinned 1024 x 1024 images (compression can increase this by up to a factor of 2). See the examples at the end of this manual.
Spinach is linked to the global Internet through a microwave bridge which communicates to the computer network on the Central Washington University campus. The IP address of spinach, the MRO data acquisition computer is "198.104.72.240". The CWU router used by spinach has the IP address of "198.104.72.1". The CWU computer folks have a firewall which disallows normal telnet, ftp, email, etc. connections into spinach. Instead, you should use the ssh (secure shell) protocol. To do this, use:
ssh -l guest spinach.mro.cwu.eduOnly ssh1 (and not ssh2) is currently supported. The contact person at CWU who is in charge of running the CWU end of the MRO microwave link is Chris Timmons. He can be reached at the following number: (509) 963-2947. His email address is:
skynyrd@tahoma.cwu.edu.The MRO 30-inch has an autoguider which can be useful for long exposures. A Lynxx 192 x 165 pixel, thermoelectrically cooled CCD is mounted on a manually operated X-Y stage on the telescope. The autoguider FOV can be moved by means of the manual X-Y stage to anywhere within a large radius centered on the FOV of the data acquisition CCD. Offsets from the center of Tbird's FOV can be made by the use of scales which are attached to each axis on the X-Y stage. The operation of the Lynxx CCD is controlled by an IBM PC, which resides in the telescope control room to the left of the main telescope controls. Use of the autoguider will be described in detail later in this document.
Filters that are currently available at MRO include a fair selection of broad, intermediate, and narrow band filters. The available filters, their bandpasses, and their approximate central wavelengths are listed in Tables 2-4. All of the filters listed in the tables are either 2 inch square or 2 inch circular filters. A number of other filters of 1 inch size are also available but not listed. See the MRO engineer for a more complete listing. Transmission curves for the Sloan filters are available in the document "The Purchase of Sloan Filters for Use at MRO". Transmission curves for the other filters listed must be obtained by asking the telescope engineer.
Central Wavelength
Bandpass
Filter
(in Å)
(in Å)
Harris U
3600
650
Harris B
4350
1000
Harris V
5400
1000
Harris R
6400
1500
Mould I
8290
1950
Washington C
3800
1100
Washington M
5050
1000
Washington T1
6200
860
Washington T2
9000
3100
Sloan u' 3530 625 Sloan g' 4860 1527 Sloan r' 6260 1342 Sloan i' 7670 1333 Sloan z' 8350 appx. 1200 (CCD dependent)
Central Wavelength
Bandpass
Filter
(in Å)
(in Å)
Stromgren u
3500
400
Stromgren v
4100
160
Stromgren b
4700
190
Stromgren y
5500
240
Wide Hß
4861
200
Central Wavelength
Bandpass
Filter
(in Å)
(in Å)
He II
4686
60
Fe II (continuum)
4750
100
Narrow Hß
4861
60
O III
5007
60
Na I
5895
3
[O I]
6300
10
H-alpha
6563
10
[N II]
6583
10
[S II]
6716
3
[S II]
6730
80
[S II]
6731
3
[S III]
9532
4.5
2 The Telescope Control Computer Software
In the control room is a 19" rack of electronics which holds the telescope display panel, the TCC, the GPS receiver, and the dome encoder display. The control room hand paddle plugs into a socket on the telescope display panel. To the left of the TCC rack lies the TCC monitor and keyboard. The TCC is found at the bottom of the 19" rack.
Before turning on the TCC you should first make sure that the telescope power is on. Likewise, when turning the TCC off you should first make sure that the telescope power is off. The telescope power is turned on by means of a key switch on the bottom of the telescope's RA skirt. When power to the telescope is on you should be able to observe three green LEDs through a large porthole on the base of the telescope. If any red LEDs are observed here, something has gone wrong with applying power to the telescope motors. The most likely cause is from turning on the telescope power after the TCC has been turned on. If red LEDs are observed, turn the telescope power off, make sure the TCC is off, and then turn the telescope power back on. If the red LEDs still persist, then call the MRO engineer.
At the top of the 19" rack are two power switches. The left switch controls the power to a fan in the rack. This fan does little for the cooling of the rack electronics and may be left off. If it is turned on, its main effect is just to add the annoying fan noise to the control room! The right switch controls the power to the dome encoder. This must be turned on. The dome encoder display is a series of 10 red LEDs and a single yellow LED just below the main TCC control panel. When the dome encoder power is on, at least one of the red LEDs should be on. If the power switch at the top of the rack is on and you do not see any red LEDs on, then something has gone wrong with the dome encoder and you should not attempt to turn on computer control of the dome position. Under these circumstances, you should contact the MRO engineer. Trying to turn on computer dome tracking when the dome encoder is either off or broken will result in a run-away dome! Manual positioning of the dome (i.e. using the handpaddle dome controls) should still function, even if the dome encoder is broken.
The 10 red LEDs on the dome encoder panel give a crude analog display of the current dome position. The first red LED lights when the dome is near the "home" position. This is the dome position where the slit cables may be plugged in to open up the dome slit. When the dome is at the "home" position, the dome slit points roughly north. The yellow LED is the actual "home" indicator for the dome. It lights up when the dome is within a couple of degrees of the true home position. Each successive red LED represents a 36 degree bin moving eastward from the home position. The dome encoder is an absolute encoder. Once it is turned on, it gives the dome position without any other initialization.
At the bottom of the 19" rack, on the left of the TCC front panel are three pushbuttons. Pressing the POWER button will boot the TCC. The TCC boot takes about 30 seconds and you should note that the TCC monitor has a separate power switch. The TURBO button on the TCC controls it's clock speed. The TCC should always be run with the TURBO option selected. Directly above the TURBO button is an amber LED which, when lit, indicates that the TURBO mode is selected. If the amber LED is not on, press the TURBO button. The third button is a RESET. The RESET button is the best way to stop the telescope in an emergency.
After the boot, the TCC monitor continuously displays the following information:
1) Telescope RA and DEC (in the current epoch coordinates)2) Sidereal and UT time
3) Telescope Hour Angle (HA)
4) Telescope Airmass
5) Telescope Zenith Angle
6) Status of the telescope tracking
7) Status of the dome tracking
The telescope and dome tracking will be off after booting the TCC. The telescope software assumes that the telescope was left in the standard park position when it first starts up. This may not be a very good assumption and observers will normally want to reset the telescope coordinates on the first night of each observing run. The standard park position is with the telescope on the local meridian at a declination of 36 degrees.
It is a good idea to turn on the filter slide power after the TCC has been booted. If this is done, then the communications to the filter slide can be checked by looking for the message "Welcome to the MRO filter slide!" to apper on the TCC monitor.
The bottom half of the TCC monitor is reserved for interactive commands and for warning messages. All of the telescope control commands are initiated by entering a single keystroke input on the TCC keyboard. Commands that move the telescope or change important telescope parameters require a capital letter keystroke. The only exception to this rule is the command that toggles between tracking and stationary telescope modes. All of the capital letter commands will ask for verification before actually attempting execution. Typing an 'h' on the TCC keyboard will cause the following menu of single keystroke commands to be printed:
C:
Set coordinates
s:
Change set rate
d:
Dome tracking on/off
S:
Change slew rate
D:
Send dome to home pos.
t:
Toggle tracking on/off
E:
Exit back to DOS
T:
Set track rates
f:
Read focus position
U:
Set UT time
F:
Set focus position
W:
Write to filter slide
M:
Move telescope
X:
Over-ride floor safety
p:
Show last precession coords
Z:
Set zenith
A brief explanation of each of these commands is given in Table 5. Only the 'W','X', 'Z', 'M', and 'C' commands require further explanation. There is a limit switch which monitors the position of the observing room floor. Normally, the software will not allow you to slew the telescope unless the observing floor is all the way down. A green light on the telescope display panel lights when the floor is down. By running the 'X' command you can override this safety feature. Use of this command requires knowledge of a password. Ask the MRO engineer for the current expert operator password.
Table 5. TCC Commands
Command
Command Description
C:
Set the coordinates to a given value without moving the telescope.
d:
Toggle the dome tracking on or off.
D:
Send the dome to the home (parked) position.
E:
Exit the MROTC program. Return to DOS
f:
Read telescope focus position.
F:
Set telescope focus position.
M:
Move the telescope to a given RA and DEC position.
p:
Print out the last precessed coordinates.
s:
Change the set rate (ie. the guiding speed).
S:
Change the slew rate.
t:
Toggle the telescope tracking on or off.
T:
Set the telescope track rates.
U:
Manually set the UT time.
W:
Write to filter slide
X:
Over-ride the floor safety switch.
Z:
Set the telescope to the zenith using the clinometer.
The 'Z' command is used in conjunction with the 'C' command to initialize the telescope's coordinate system. The telescope does not use absolute encoders to track its position. When telescope power is removed the hardware forgets where things are. Users are therefore required to initialize the telescope coordinates at the start of each observing run. Crude coordinates may be set by pointing the telescope toward the zenith and then typing the 'Z' command. On the base of the telescope there is a bubble level that can be used to determine when the telescope is at the local zenith. However, under normal conditions, it is not necessary to refer to the bubble level when setting the telescope to the zenith. In the filter slide box there is an electronic clinometer which the TCC is capable of reading. This clinometer has a working range of approximately 5 degrees from zenith. When setting the telescope to the zenith, users need only place the telescope within range of the clinometer; which can normally be done by eye without referring to the bubble level. The telescope will then find the zenith using the clinometer when the 'Z' command is typed. Coordinates set in this manner are normally accurate enough to allow a user to place a bright star in the FOV of the finder telescope by executing a normal computer move of the telescope (ie., an 'M' command). Once this is done, the observer should use the finder telescope to move the chosen bright star to the center of the CCD's FOV. Note that currently the center of the CCD's FOV is not in the center of the finder's FOV. You will see a red reticle circle in the finder. The center of the CCD's FOV is at the 7 o`clock position just inside the reticle circle. A quick test image will verify the placement of the star. When the star has been appropriately centered in the CCDs FOV, you can use the 'C' command to reset the telescope coordinates to the known coordinates of the star. The 'p' command will show the last precessed coordinates.
Observers can move the telescope manually with the hand paddles or they can request that the computer move the telescope given a set of target coordinates. When the 'M' command is used to move the telescope, the observer is first prompted to input the epoch of the coordinates that he will be entering. After entering the RA and DEC, the computer will precess the input coordinates to the current epoch, display the precessed coordinates on the TCC monitor, and then move the telescope. Several safety features are built into computer slews of the telescope. Movements to zenith angles greater than 80 degrees are not allowed. The telescope horizon limit switches are set for 82 degrees. Manual moves will allow the user to run the telescope all the way to the horizon limit switches. If the observing floor is not all the way down, the computer will not move the telescope. Warning messages will be printed on the TCC monitor telling the observer why the telescope could not be moved.
There are two possible causes for failure to acquire a star in the finder's FOV after the telescope zenith has been set. The first is inaccurate use of the bubble level. If you do not carefully center the bubble, then the star can be off by 2 or 3 finder FOVs. The second is that the UT time of the TCC is not set properly. Below we discuss how to check the UT setting of the TCC.
It is a good idea to check that the UT time displayed on the TCC monitor is accurate. An accurate value for the UT time can always be found on the LCD display of the GPS receiver in the telescope control rack. The synchronization of the TCC time with spinach's clock should keep it well within 1 second of the UT time displayed on the GPS receiver at all times. If, for some reason the GPS clock has been disabled, you can also tune the radio on the observing floor to a WWV wavelength (5, 10, or 15 MHz) and to use the audio signal to verify the UT time on the TCC. Using the observing floor radio and the telescope control program's 'U' command, it is possible to manually set the UT time to within the nearest second. You can check spinach's clock against the local time server with:
guest@spinach:~> ntpdate -q asgardor if there seems to be a problem with asgard, against orca in Seattle with:
guest@spinach:~> ntpdate -q orca.astro.washington.eduThe resulting offsets should be a very small fraction of a second.
There are two useful things to know about the operation of the telescope hand paddles. First, circuitry in the display panel protects the telescope from conflicting hand paddle commands (eg. pushing the N and S controls simultaneously will not hurt the telescope). Second, observers should be aware that it is easy to be confused by the operation of the hand paddles' "set/slew" switches. The "set/slew" switch determines the speed of the manual slew motions. If either hand paddle has its switch in the "slew" position, then the telescope will run at "slew" speeds, regardless of the setting at the other hand paddle. It is highly recommended that users keep the observing floor hand paddle in the "set" position as much as possible to avoid confusion.
Finally, we must discuss the use of the 'W' command. This command allows you to send low-level commands directly to the filter slide without going through the data acquisition software on spinach. Most of these low-level commands consist of one or two characters and there are many which are not documented here. To find out what these are you need to refer to the document "The MRO Filter Slide". Some of these commands can cause significant problems with the filter slide if not used correctly. You should not be playing with these commands without good reason and permission from the observatory engineer. There are, however, six commands which are very useful to know about and which are safe to use. These commands are listed in Table 6.
Table 6. Low-Level Filter Slide Commands
Command
Description
Examples/Returns
mx
Move filter slide to position x
m1 / done
Mx.xx
Tilt filter slide to x.xx degrees
M1.21 / done
s
Get status of filter slide position
s / 1,0,5
t
Get status of tilt mechanism position
t / 4.32,4450,248
o
Reset origin of filter slide (moves to m1)
o / done
O
Reset the origin of the tilt mechanism
O / done
There are three numbers returned from a successful 's' or 't' command. The first of these numbers shows the position where the filter mechanism thinks it is. The second number is the raw encoder counts that correspond to that position. And the last number is the current value of the tab sensor. In the example given in Table 6, the return for the 's' command shows that the filter slide thinks it is at filter position 1 with a raw encoder reading of 0 counts and a tab sensor reading of 5. The example return for the 't' command shows a current tilt of 4.32 degrees, a raw encoder reading of 4450 counts, and a tab sensor reading of 248.
The tab sensor readings can be used to verify that the filter slide is at an appropriate position. The tab sensor readings run from 0 to 256. A low value means that the light from the sensor is completely blocked by a tab. Any value over about 240 indicates that the sensor is completely open. All appropriate filter positions should show a tab sensor reading less than 20.
3 The Data Acquisition Software
The software that users need to become acquainted with falls under three categories. First, since spinach's native operating system is Linux, an observer needs to develop an understanding of how basic things are done in Linux under the window environment. This is especially critical for proper use of the tape drive. Second, the user must develop a familiarity with how commands are run in the IRAF environment. This is essential because all of the CCD commands are IRAF commands. Third, a user must have a basic understanding of how to run the PC based autoguider software. In the last section of this document we will provide some examples of how a user might interact with this software when making observations. In this section we will provide a basic overview of these three software packages. If a user is already familiar with Linux and IRAF, the quickest way to become acquainted with the data acquisition software is to first turn to the examples section of this document.
3.1 The Linux environment
An account called "guest" is reserved for the use of all MRO observers. Users should check with the MRO engineer for the current password of this account. We will assume here that the guest account has a password of "usrpsswd". The login procedure in Linux is similar to that found in many other operating systems. A "login:" prompt expects the user to enter an account name. If a password is necessary the computer will give a separate "password:" prompt. The standard observing login sequence would go as follows (the user's response is given in italic type):
spinach login: guestpassword: usrpsswd
Upon successful entry of the account password, the default Redhat Linux windows manager (Gnome) will start up. Several icons should appear at the bottom of the screen.
After logging in, one of the icons at the bottom of the screen will be the footprint of a Gnome. (OK, I didn't make this up, blame Redhat Linux for that one). Right-clicking on the footprint will display several sub-menu items, one of which is called "Favorites". Right-clicking on "Favorites" will display another list of sub-menus. Select the item "Observing" in this list and you will find all of the critical links for IRAF observing at MRO.
Programs in the "Observing" sub-menu include a Tbird Command Window, a Mustang Command Window, Analysis Window, and DS9. Until further notice, DS9 will be the only image display program available at MRO. Programs such as ximtool do not work properly under Linux. DS9 is fairly intuitive, but if you need help running it, look up its help pages on the web with a Google search. The web browser Netscape is available under the "Favorites" menu. Also note that under the "Favorites" menu is a link to the "xterm" program. It is often useful to have an xterm window available for general file manipulations or for setting up an ftp session to transfer your data.
When you use the IRAF command "display" to view and image with DS9, you may find that the orientation of the image does not match that seen on the Tbird monitor. To make the two monitors look alike you need to have the settings "Invert Y" and "90 deg" selected in the "Zoom" menu found at the top of the DS9 window. Note that these settings need to be set for each frame of the DS9 window! Thus, if you display an image in frame 1 with the command "display 1 imagename" and then set the Y invert and 90 degree rotations in the "Zoom" menu list, you may find that if you use the command "display 2 imagename" that things will once again look unfamiliar.
The Tbird and Mustang Command Windows are links to xgterm windows set up to run IRAF "cl" sessions that have been customized to run the respective cameras. The Analysis Window is a generic IRAF "cl" session which can be used to analyze and inspect images while taking data with the other windows. Note that if you know how, the analysis window can be configured to run the cameras, but I suggest that you not do this. It can create significant operator confusion to have more than one window controlling the camera. For this same reason, its not a good idea to have more than one Tbird or Mustang Command Window open at one time. But, if you want to confuse yourself, feel free! Just make sure that you don't call me in the middle of the night for help if you insist on doing this!
Note that the difference between the Tbird and Mustang Command Windows is not just the title given to each window. These commands utilize two different IRAF uparm directories which have been set up to run either Tbird or Mustang.
It is important to realize that the CL environment is essentially its own operating system which runs on top of the normal Linux shell. Many IRAF commands simply duplicate the function of the native Linux commands. For example, the IRAF "dir" command and the Linux "ls" command do essentially the same thing. This duplication occurs because IRAF was designed to be usable on machines with different native operating systems. In principal, all one needs to learn are the IRAF commands; in practice its a very good idea to learn both ways of doing things. In the MRO environment that you will be using, several, but not all Linux commands will be recognized by the IRAF shell. Hopefully, this will be more convenient than confusing.
When you have a screen or window responding with the "cl>" prompt, the commands that the computer expects to see are IRAF commands, not normal Linux commands. When the computer responds with the machine name prompt (i.e. "guest@spinach:~>"), then it is expecting Linux commands. Sometimes, it is easier to accomplish a task in the Linux environment rather than in the CL environment. To execute a single Linux command from a CL window you can always use the "!" escape mechanism. By starting your command with the "!" character you force the computer into Linux mode. Anything typed after the "!" will be interpreted as a Linux command. One way of getting the computer to accept multiple Linux commands is to type "!tcsh" after the CL prompt. This opens another "shell" which will be active until you type "exit" or control-D. When you exit from a shell invoked with the "!tcsh" command you will be left back in your original IRAF environment. This is a bit awkward; you are better off just using another/new xterm window.
In the tcsh environment, you can use the [Up] and [Down] arrow keys to scroll through the command history as well as edit (with [Left], [Right] arrows, Delete, etc.) previous commands and reexecute them. In the IRAF environment, you must first press 'e' and then [Enter] before being able to scroll through and edit the command history.
To conclude this section, we would like to present a list of Linux commands which will be helpful to getting you started and will hopefully act as a quick reference. To find detailed information on any Linux command all you need to do is type "man command_name", where "command_name" is the name of the command of interest. If you do not remember the command name, then you can type "man -k keyword" where "keyword" is a word or phrase that you think should be related to the command of interest. For example, the command "man -k list" produces a rather long listing, one line of which is:
ls (1V) - list the contents of a directoryThe first portion of this line gives you the name of the command. In parenthesis you find the manual section in which the command listing is found. The last portion gives you a one line description of what the command does. For more information on the "ls" command you could then follow this with "man ls". The first line of each manual page gives you a listing of what you need to type to invoke the command. Things shown in square brackets are optional command line parameters. Things preceded by a minus sign are usually "flags" which tell the program to function in a particular way. Sometimes flags are followed by flag arguments (like file names), but usually a flag just toggles some program behavior on or off. In any case, the effect of each flag on the program is always detailed in the main body of the requested manual pages.
Table 7 is meant to be a quick reference to Linux commands that you will find useful. Note that for the tape drive commands it is recommended that you closely follow the commands given in the examples section of this manual in order to avoid costly mistakes in transferring your data to tape. Observers can use the native IRAF routines to write data directly to the tape drive, although unix tar commands are usually preferable. Examples of the IRAF tape drive routines are also given in the examples section of this manual. Readers interested in the details of the IRAF tape commands should consult the IRAF 'help' files for routines 'wfits' and 'rfits'.
Table 7. Common Linux/Unix Commands
Command
Command Description
cd dir
Change into a subdirectory called "dir"
cd ~
Change into your home directory
cd ..
Move up one level in the directory tree
cd /data/guest
Go to the main storage directory named "/data/guest"
date
Display the current time and date (this should always display the local time)
date -u
Display GMT
df
Display the amount of disk space used and available.
env
Display the value of all your current environment variables.
exit
Terminate a shell window
kill -9 411
Kill the program with a Process ID number of 411 (use the "ps" command to get the PID number)
ls
List the contents of the current directory
ll
Long ls listing including sizes and dates
lpq
Display the printing queue for the default printer
lpr file
Print the contents of "file" on the default printer
lprm 5
Remove job number 5 from the printer queue.
mkdir dir
Make a new directory named "dir"
more file
Display the contents of "file", one page at a time.
mt rew
Rewind the magnetic tape
mt fsf 2
Forward space over two files on the magnetic tape.
ps auxw
Display the complete process queue (show the status of all running programs).
pwd
Display the current (working) directory
rm file
Remove "file" from the current directory (there is no recovery of "file" once this is done!)
rm f*
Remove all files in the current directory that begin with the letter "f".
rm *
Remove all files in the current directory.
setenv DISPLAY popeye:0
Set the DISPLAY environment variable to popeye:0
tar -cvf /dev/nst0 .
Create a tape archive consisting of every file in the current directory.
tar -tvf /dev/nst0
Print a table of contents of the tape.
tar -cvf files.tar night1
Create a disk "tar" file called "files.tar" which contains the subdirectory night1/ and all files in it.
vi file
Edit or create the contents of a file called "file" using the "vi" editor.
nedit file
Edit or create the contents of a file called "file" using the "nedit" X GUI editor.
ed file
Edit or create the contents of a file called "file" using the "textedit" GUI editor.
3.2 The IRAF Data Acquisition Environment
3.2.1 Loading the CCDACQ package
We do not intend to give here a description of the IRAF command language environment. Such a description can be found in the document "A User's Introduction to the IRAF Command Language" by Shames and Tody. See the MRO engineer if you need a copy of this document. We do wish to give a description of the IRAF data acquisition software that is in use at MRO. The original software package is called "ccdacq" and was written at Steward Observatory by Skip Schaller. This same package has been adapted by the folks at Kitt Peak and is running there under the nickname of ICE which stands for IRAF Control Environment. At MRO, although we have made some modifications to the original package, we retain its original name out of respect for Skip Schaller. Upon entering the IRAF environment, a user may load the CCD data acquisition software by first loading the "local" package, and then loading the "ccdacq" package. To do this simply type in the package names as shown below (user input is shown in italics):
cl> mrobswap ccdacq. pavg
mro> ccdacq
abort detector mores resume tests comps flats observe stop zeros
darks instrument pause telescope
cc>
As is standard in IRAF, the computer responds to each request to load a new package with a list of routines that are available in that package. Note that the computer prompt changes to reflect each package that is loaded. Despite the fact that ccdacq contains 14 separate commands, you will find that almost everything that you will want to do with the detector can be accomplished by the single routine "observe". The operation of this routine will be described in a subsequent section of this document.
All of the ccdacq routines are described in the online "help" facility which is invoked by commands like:
cc> help moreswhere "mores" is the name of the routine for which you wish information. In addition to the online help, all of the help information (including this document) is available in a loose leaf binder at MRO entitled "IRAF Data Acquisition".
3.2.3 Using the observe command
The observe command is designed to integrate the operation of the detector, the telescope, and any instrumentation used with the detector such as the filter slide or the spectrograph. By design, this one command can change filters or move spectropgraph optics if this is appropriate, take an exposure of the desired length, and record the data to disk with all of the appropriate time, telescope, instrumentation, and detector information stored in the image header. The data acquisition computer queries the TCC for information that it needs for the header.
To run the observe program you will normally complete the following three step procedure.
- Edit the parameter files. Once a night you may want to edit the weather condition variables in the parameter file telpars. Each filter change you will want to denote by editing "filters" in the parameter file instrpars. For each format change in the CCD you will need to edit the parameter file detpars.
- Move the telescope to your object.
- Type "observe"and interactively answer the queries posed.
3.2.4 The parameter filesTo accomplish its tasks the observe command retrieves information from four separate data bases. In "IRAFese", these data bases are called "parameter files". There is a general observing parameter file and a parameter file each for the detector, the telescope, and the instrument. These files can be altered or viewed simply by typing their names at the CL prompt. Once the files are opened (by typing their name), a carriage return will move the cursor to the next parameter without altering the current variable's value; typing followed by a carriage return will alter the current variable; a control-k will return the cursor to point to a previous value; and a control-d will exit back to the CL prompt.
The names of the parameter files are: obspars, detpars, telpars, and instrpars. The RA, DEC, and focus position are set in the telpars parameter file and the filter position is set in the instrpars parameter file. Although there are a large number of settable parameters, you should find that the vast majority of these parameters will be set or checked by you only once at the beginning of your observing run and then never altered.
Below we list the variables which are found in each of the parameter files. We give what should be standard settings for each parameter along with comments on what these parameters do. In these lists parameter values given as "*" have no standard values. An entry of " " indicates that the standard value is to have nothing in this field. Keep in mind that parameters that do not begin with a parenthesis will be prompted for when the "observe" command is run. It is usually a waste of time to set these variables in the parameter file. Some of the variables are unused by the MRO software, but are retained in the parameter files because they are used in the Steward and Kitt Peak versions of the software. A "mode" and "nargs" parameter exist in each parameter file, but are not shown in the following lists. These parameters are standard IRAF variables that deal with how the command is called and how the program will query for variables. We suggest that you keep "mode" set to its standard value of "ql" and nargs set to "".
Obspars contains variables which control the general observing environment. It includes the following parameters and standard values:
Parameter Setting
Parameter Description
exposure=
*
Exposure time (in seconds, fractional values are OK)
imagetyp=
object
Image type (other possible values: standard,dark,flat,zero,focus,nofile)
objectti=
*
Object title (Up to you! This doesn't set the file name!)
(rootnam=
a)
Root of disk file name (e.g. for a0001.fits,"a"=root)
(sequenc=
1)
Sequence number of file name (e.g. for a0001.fits, "0001"=sequence #)
nrvrows=
*
UNUSED BY MRO SOFTWARE
nfexpo=
*
Number of focus subimage exposures per focus observation
shtype=
detector
Shift type (UNUSED AT MRO)
foctype=
telescope
Where the focusing will be done
fstart=
-10000
Starting focus value (when doing a focus observation)
fdelta=
4500
Focus increment between focus subimages
(fdelay=
1)
Delay between focus exposures (in seconds)
(fzoom=
4)
Zoom factor for the real time focus subimage display
(pixtype=
u)
Data type of IRAF image pixels (u=short integer)
(observe=
" ")
Name of observer(s)
(comment=
" ")
Comments to include in image header
(comfile=
" ")
Observer header comments file (UNUSED AT MRO)
(obsinfo=
" ")
Observer header info file (UNUSED AT MRO)
command=
" ")
Post-processing command (e.g. if you want to immediately display all images acquired, you can set this to "display %s 1 &")
(verbose=
yes)
Give real time reports on the tasks being done
(debug=
no)
Display debugging information
Detpars is the parameter file which you edit to alter the CCD format. The detpars files for Tbird and Mustang differ only in the specification of the detector name. Below we show typical detpars settings for Tbird. For Mustang, the detname parameter would be changed to "mustang":
Parameter Setting
Parameter Description
(firstco=
1)
First CCD column to use in output subimage (always in unbinned pixels)
(lastcol=
1024)
Last CCD column to use in output subimage (always in unbinned pixels)
(firstro=
1)
First CCD row to use in output subimage (always in unbinned pixels)
(lastrow=
1024)
Last CCD row to use in output subimage (always in unbinned pixels)
(colbin=
1)
Column binning factor
(rowbin=
1)
Row binning factor
(preflas=
0)
Preflash time (UNUSED AT MRO)
(gain=
90)
Gain used in CCD A/D conversion
(detinfo=
" ")
Detector header info file (UNUSED AT MRO)
(detcap=
ccdacq$detcap)
Detector capabilities file (Required to define the detector characteristics. Don't alter this setting!)
(detname=
tbird)
Name of the detector being used
The user may find helpful a few extra comments concerning the "gain" variable. For both Tbird and Mustang, you can speed up the readout of the array by specifying lower numbers to the gain variable, but only at the cost of a higher number of electrons per A/D unit and a higher read noise.
For Tbird, the best gain setting depends on your observing conditions and priorities. In general, the trade-off comes between low-light sensitivity and dynamic range. If you have observations which will always have very faint sources, you probably want to stay with the standard setting of gain=90. If you will often have very bright sources in your field of view, you might want to go with the high dynamic range settings of 15 or 20. A compromise setting would be to have gain=50. The details of each of these settings is given in Table 8 below.
Table 8. Tbird's Standard Gain Settings
Observing Conditions
Gain Setting Binning System Gain, e-/ADU Read Noise, e- Low-light Level Settings 90 1x1 2.94 2.88 90 2x2 2.83 2.88 Compromise Settings 50 1x1 4.55 3.39 50 2x2 4.25 3.13 High-Dynamic Range Settings 20 1x1 7.18 2.82 15 2x2 7.50 2.94 For the adventuresome observer who wishes to use a non-standard gain setting we give the relationships between the "gain" variable, gain, the system gain, G, and the readout time per pixel,tr, for Tbird:
and
For the default gain setting of 90, it takes approximately 63 seconds for the controller to read out the chip. Setting gain to 45 decreases the read time to 43 seconds, only a modest improvement. Users should also remember that these read times only represent the time it takes to transfer the image from the chip to the CC200 controller. If an image file is to be recorded, you also must account for the time it takes to transfer this image to the data acquisition computer.
Roughly speaking, the system noise increases as the gain setting decreases. Plots of the system noise vs. gain setting and the read-noise vs. gain setting are shown in the engineering report on the new camera installation. Fits to these data for 2x2 binning are given by the equations:
where G is the system gain, g is the gain setting in IRAF, and R is the read-noise. Similar equations for the case of 1x1 binning are shown in the new camera installation graphs. Note that in the equation above for the read-noise is only an approximation and there is a significant and real departure from this equation at a gain setting of 15. At this point the read-noise is quite a bit lower than one would predict from the equation above. Likewise, for 1x1 binning the read-noise is very low at a gain setting of 20. This is why these settings are preferred for the high dynamic range settings.
For Mustang, the read noise and gain for the default gain setting of 90 are 3.8 electrons/ADU and 12.3 electrons, respectively. And, the relationship between the gain variable and the system gain is given by
The readout time per pixel is the same as Tbird. Again, the system read noise increases as gain decreases. At gain settings of 45, 90, and 150 Mustang's system read noise is 13.6, 12.4, and 11.9 electrons, respectively.
Telpars contains variables related to the telescope settings and environment. Most of the parameters in this file are set automatically by the telescope routine and do not need to be altered by the user. This file includes the following parameters and standard values:
Parameter Setting
Parameter Description
(dateobs=
" ")
Date of observation (you don't need to set this because it will be set automatically from the computer's clock)
(ut=
" ")
Universal time (set automatically!)
(st=
" ")
Sidereal time (set automatically!)
(ra=
*)
Right ascension of current image (set automatically!)
(dec=
*)
Declination of current image (set automatically!)
(epoch=
*)
Epoch of RA and DEC (set automatically!)
(ha=
" ")
Hour angle of current image (set automatically!)
(zd=
" ")
Zenith distance of current image (set automatically!)
(airmass=
" ")
Airmass of current image (set automatically!)
(telfocu=
" ")
Telescope focus position (set automatically!)
(rotangl=
" ")
Instrument rotator setting (UNUSED AT MRO)
(pressur=
" ")
Barometer reading (UNUSED AT MRO)
(windspe=
*)
Wind speed (UNUSED AT MRO)
(humidit=
*)
Humidity (UNUSED AT MRO)
(seeing=
*)
Seeing estimate
(telinfo=
" ")
Telescope header info file (UNUSED AT MRO)
(telcap=
ccdacq$telcap)
Telescope capabilities file (Required to define the telescope parameters. Don't alter this!)
(telname=
mro30)
Telescope name (Required! Don't alter this!)
Instrpars contains variables which describe the settings of the instrumentation. It is through settings in this parameter file that you are able to control either the automatic filter slide or settings of the spectrograph. Everytime an exposure is taken by running the "observe" command, the parameters in this file are checked. The filter slide and spectrograph mechanisms are moved prior to an exposure being taken. THERE IS NO WAY FOR THE NORMAL USER TO MOVE THE SPECTROGRAPH WITHOUT TAKING AN IMAGE. Contact the observatory engineer if you need to do this on a regular basis, otherwise "nofile" exposures may be taken to move the spectrograph without recording an image.
The filter slide's instrpars settings
The normal way to control the filter slide is through the observe command and through use of the appropriate instrpars settings. However, the user may move the filter slide without taking an exposure by use of the TCCs "W" command. This command allows a user to write a low-level command directly to the filter slide. The use of the TCC "W" command is documented here and the low level filter slide commands are found in the document "The MRO Filter Slide".
There are only four critical variables that control the action of the filter slide: filters, tiltpos, instrca, and instrna. The parameter fts is available for use, but can be left blank. For the filter slide the other variables in "instrpars" are unused. The filter slide position is set by "filters". Setting this parameter to a number between 1 and 6 will cause the filter slide to be moved to the corresponding filter position. The tilt of the filter is set by the parameter "tiltpos". The tilt may be any number between 0 and 15.5 degrees. The tilt angle of the filters is accurately set to within 0.02 degrees. Below we will return to the issue of using tilts with filter settings.
The parameter "instrna" sets which instrument will be run during an exposure. At MRO the only possible settings for this parameter are "fslide", "sp300i" and "test". We will deal with the affects of setting this to "sp300i" in the next section. To move the filter carriage "instrna" must be set to "fslide". If you wish to take a long series of measurements without moving the filter, you can turn off the code which moves the filter slide by setting "instrna" to "test". If "instrna" is set to "test" the "filters" and "tiltpos" information are still included in the image headers, but no actual attempt to check the filter position is made by the software. Typical settings to run the filter slide are shown below:
Parameter Setting
Parameter Description
(filters=
2)
filter bolt position (this runs from 1-6)
(slitwid=
)
slitwidth
(filtnam=
)
filter name
complamp=
comparison lamp (optional)
(probepo=
)
probe position (UNUSED AT MRO)
(grating=
)
grating
(tiltpos=
0.0)
tilt position
(decker =
)
decker (UNUSED AT MRO)
(instrfo=
)
instrument focus (UNUSED AT MRO)
(wavelen=
)
wavelength
(dispaxi=
)
dispersion axis (optional)
(fts=
home$filter.names)
filter translation file name (optional)
(instrin=
)
Instrument header info file (UNUSED AT MRO)
(instrca=
ccdacq$instrcap)
Instrument capabilities file
(instrna=
fslide)
Instrument name
(mode=
ql)
Note that the default value for "instrna" is "fslide". If you ever change that to test, be sure to set it back.
The status of the filter slide motions are displayed on the TCC monitor. For a successful change of the filter slide, the following sequence of messages will be displayed on the TCC monitor:
"Moving to filter position 2""Move to filter position 2: done"
"Moving to tilt 2.00"
"Move to tilt of 2.00: done"
The filter slide takes approximately 8 seconds to move one filter position. It takes approximately 4 seconds to move 1 degree in tilt. If excessive time passes between the initial "Moving to..." message and the corresponding "...done" message, this is an indication of problems with the filter slide.
To date the most common problem with the filter slide has to do with errors in the RS-232 communication link. If the slide appears to be hung up, abort the exposure and try running it again. You will probably have to rerun it twice in order to clear first the IRAF abort warning and then the communication buffers between the TCC and the filter slide. If the problem is with the RS-232 link, then in the process of rerunning the observe command you will get the message "Bad command:..." on the TCC monitor. If this does not appear, then it indicates that the filter slide is having serious problems. Under these circumstances you should contact the telescope engineer. For safety of the instrumentation, the filter slide power should be turned off and the filter position should be checked visually by removing the filter cover to see if its in the proper position.
As an alternative to entering the "instrpars" parameter file and changing its settings, the command script "fobs" has been defined in the user's home directory. "Fobs" will interactively prompt you for a filter position and then it will run "obs". If you are changing filters with every exposure, this is much more convenient way to run than by editing "instrpars".
