GBT Remote Observing Manual

Make sure to email the GBT telescope operator ( the day before you are schedule to observe to let him that you will be doing the observing (and remotely) and at what telephone number you can be reached.


This starts 30 min. before the scheduled start time.

See Remote Observing on the GBT for detailed instructions.

-You need two programs to do remote observing:
1) A Terminal Emulator such as Terminal, X11 or Putty
2) A VNC viewer. "Checking of the VNC" for macs (download from here). For PCs use TightVNC or RealVNC.

1.) SSH to GB.

On your computer open a terminal or xterm and ssh to first and then to tiania.

    computer % ssh  [enter password]
         stargate % ssh titania                        [enter password]

2.) Start the VNC Server

Now start the vncserver on titania with the right geometry for your screen.

    titania% vncserver -geometry 1200x800

  • Make a note of the number it returns, i.e. ":3". This is your display number that you'll need later on.

  • The "-geometry 1200x800" tells the VNC Server how large of a window you want. You might have to play around with this to figure out the best window size for your computer.

  • To stop the VNC server type:

    titania% vncserver -kill :3

  • Make sure you use the display number for your session (that was given to you when you started the VNC server)

3.) Start SSH tunneling

    computer%ssh -N -C -L

4.) Start the VNC viewer on your computer
  • Start "Chicken of the VNC" (or the PC version).
  • Open a new connection.
  • Put the right vncserver session number in the "display" box and then "localhost:590#" (where # is your vncserver session number) in the server/host type.
  • It should ask for your password (this is your VNC password), and then a window should pop up. I would not run it in "Full Screen" mode, so click on "cancel" if it asks.

If you are using a Mac then you might have to modify the way the mouse buttons working "Chicken of the VNC". To do this go to "Connection" and "Connection Profiles". Click on the "Emulation" tab. The way I have it set up is "Center Mouse Button=Modifier Click", Modifier Key=Option, "Right Mouse Button=Modifier Click", Modifier Key=Command. So you need to hold down the option key and click to do a center click and hold down the command key and click for right click.

If the window does not open
There might be too many displays running with the vncserver. If the display number that you got is larger (9 say) then that's probably the problem. You'll need to kill all the other displays that are running (and sending signals nowhere). Do the following. Run the kill command
(vncserver -kill :#, substitute the # for the display number) on all display numbers less or equal to yours all the way down to 1. So if your display number is 9 then kill 9,8,7,6,5,4,3,2,1. Then try going through the above steps again to start the vnc window.

5.) Start "Talk and Draw" so you can chat with the operator.

b) Start the "Talk and Draw" program

    titania% cleo talk_n_draw

-In 10-30 seconds a new window should open up that with the "Talk and Draw" program.
-The top part of the panel shows what people have written
-To communicate type in the bottom panel and hit return. You should see the text appear in the top panel in your corresponding color.
-I like to have the chat window show up on all dekstops. To enable this, click on the button in the upper-left hand corner of the chat window and select Desktops->to all desktops. Now it should appear in all desktops.

6.) Start Astrid, after confirming with operator that it is ok to start observing.

  • Start astrid.

    titania% astrid &

  • When it starts up it will ask you which mode you want to run it in. Select the last option "Working online with control of the telescope".

7.) Start gbtstatus.

  • There are several ways of doing this. I normally use option 1.

Option 1.) Using the Cleo "Status" and "Scan Coordinator" windows.


(b) Under the "Launch" menu select "Status". That will bring up a fancier version of the gbtstatus window.

(c) You can also start the "Scan Coordinator" by selecting "Scan Coordinator" from the "Launch" menu. This gives you more information about each scan, such as the file it's writing to and the time the scan was started and finished.

You can make any cleo window smaller by pressing CTRL+ALT+"-" or larger by pressing CTRL+ALT+"+".

Option 2.) For doing this on the VNC, simply type gbtstatus in a terminal window on the VNC.

Option 3.) There is a gbtstatus tab in Astrid that gives the same information.

Option 4.) For doing this on your own computer:

    computer% ssh

b) Start the gbtstatus program that tells you what the telescope is currently doing.

    prospero% gbtstatus

8.) Start GBTIDL.

  • Start a new terminal in the VNC (probably on a new desktop) and start gbtidl.

a) Start gbtidl

    titania% gbtidl

b) Once you've started observing type "online" so we have access to the current data

    (titania) GBTIDL> online

c) Type "summary" to see a summary of the scans that have been observed.

d) Type "getfs,scan_number" to view a scan (replace "scan_number" by the actual scan number in the first column of the summary output).


  • We are using very large RALongMap mapping scripts that should run for many hours.
  • Before a session a new mapping script for that session needs to be created and saved to the database. This is quite simple and normally means just making a copy of the script from the last session and making some small edits.
  • Check the logbook and see where the last session left off and the new mapping script on the next scan.
  • Make sure that there are enough scans to last for the entire session. Setup takes about 20-30 minutes and each scan takes a little less than 18 minutes.
  • We want to balance every 5 scans/rows and use the closest balance position (one every degree).


Now that we're all set up we can start observing.

1.) Enter in the information our project and observing session

b) Enter session number (should have incremented automatically)

c) Select your name under "observer" (it's ordered alphabetically by the first name).

d) Select the current operator. I normally have to ask them what their name is in the "Talk and Draw" window. BEWARE, there is a bug, you can't select the first name unless you select another one first.

2.) Start feeding it scripts!

-This is the general order of an observing run:



There is a new feature of Astrid that allows you to view the raw spectra. In the "Data Display" tab there is a new tab called "Spectra Line Beta". It should show you the latest raw spectra. You can select Reference/Cal, Signal/Cal, Reference/No Cal, Signal/No Cal and the polarizations (XX or YY). I've been viewing Reference/Cal and both polarizations. This gives you a good sense of the baselines.

You'll want to view the data every once and a while. When in GBTIDL make sure that you are "online" if you haven't done so already. Type "summary" to view the scans that are completed.

To View a scan type:

  GBTIDL> getfs, ##

where ## is the scan number. By default it plots the whole scan at once, with polarization 0 or YY. You can select a specific integration (one of 37 per scan) by adding "intnum=##". You can also select a different polarization by adding "plnum=#" where # is 0 or 1. For example, if you want to see scan 13, integration 15 and polarization 1 (XX) you would type:

  GBTIDL> getfs,13,intnum=15,plnum=1

You can box average channels by typing:

  GBTIDL> boxcar, ##, /decimate

where ## is the number of channels you want to box average. I normally use 7, because that brings the resolution to ~1 km/s.

To take out the baseline you want to select the regions first that it uses to make the fit. Type "setregion" and left click on the plot (once for the beginning and another for the end of each region). Right click to get out. Then set the order of the polynomial by typing "nfit,#" (3 is a good starting point). Type "bshape" to show the fitted baseline and "baseline" to remove the baseline and replot.

For more help on any command type "usage,'command',/verbose"

There is a GBTIDL user's guide:

and full documentation:


At the end of a session, one of the bricks is likely to get cut off. To do this properly hit the "Pause" button in Astrid. That will finish the current scan. When it's done hit the "Abort" button and the "Pause" button again.

Let me operator know in the "Talk and Draw" window that you're shutting down. Quit Astrid by pulling down the "File" menu and hit "Exit". Click the "Quit" button on the botton of the "Talk and Draw" to quit that application. Hit "q" to quick gbtstatus. Type "exit" to quit GBTIDL. Exit all terminals.

Now you need to kill the VNC server on prospero. In the terminal on your computer type "vncserver -kill :3" where you put your number instead of "3". Then close your terminal.


Please keep a log in the electronic logbook on this wiki page.


If any time was lost due to technical difficulties then the telescope operator should log this in the operator's observing log.
You can also email the helpdesk about any lost time.

Important Numbers

(304) 456-2341 Telescope Operator
(304) 456-2346 Telescope Operator (speaker phone)
(304) 456-2275 Toney Minter
(304) 456-2302 Jay Lockman
(434) 249-6845 David cell
(434) 296-7618 David home

GB Observing Information: (old)

GBT Staff List (with contact information):

GBT Observing Schedule Website:

How to Reduce Frequency Switched Spectra:

-- DavidNidever - 2011-08-25
Topic revision: r3 - 2013-07-20, KatBarger
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