This is a quick step-by-step guide to making an OTF map at the FCRAO 14m telescope. I wrote it for my own use, but I hope it comes in helpful for others. However it is by no means complete or necessarily accurate. I make no attempt to explain why in this how-to. Please consult the Quabbin User's Manual available online or in the telescope control room for full instructions, or the On-the-Fly and Dual-IF manuals available online at http://www.astro.umass.edu/~fcrao/library/manuals/.

1. Remote Observing

• Log onto "fcrao"

  > ssh -l observer fcrao.astro.umass.edu

  and enter the password at the prompt.

• start the terminal emulation program by typing "mterm"

  > mterm

  It will ask you for some details (name, phone number, email address). This is important in case there is a problem with the telescope, and the support staff need to contact you.

• After entering your details it will prompt you to press enter to begin. After you have pressed enter you will be faced with a screen with some random looking numbers scattered over it.

  Press any key to obtain a prompt. ?NET should appear in reverse video at the bottom of your terminal window.

  Type "REFR" (short for refresh) in upper case and press return.

  ?NET REFR

• The screen should now update, and display the telescope control and monitoring screen.

• Before you are able to carry out any active commands remotely you will be prompted for a username and password. Enter your own name and the password in UPPER CASE.

2. The Control and Monitoring Screen

3. Starting up

When you start, the telescope will likely be in "HALT" mode. This means it is parked and not tracking or slewing.

To obtain a command prompt press any key. This must be done before any commands can be entered and is assumed from here on.

• Set the operator initials:

  ?NET OPER NR

• To start the telescope tracking and enable it to slew to your source type "POINT" in upper case and press return.

  ?NET POINT

4. Pointing and Focussing

• Select a suitable pointing source from the list.

• Enter this as the required target source e.g.

  ?NET MAIN NAME RCAS

  for the pointing source "RCAS"

  The source name should appear in the top second-left panel of the display, and the telescope will start slewing to the source.

• Set the reference (off) position:

  ?NET SAME REF AZOFF -0.2

• Select the correlator parameters and bandwidth:

  ?NET IFTYPE 2
  ?NET STAR QTUNE
  ?NET CONF 2 RESET
  ?NET CONF 1 COR LINE SIO-4 LSB
  ?NET CBAND 50

• Check and set the autopoint parameters:

  ?NET APOI
  ?NET APWEA 1
  ?NET APMO 2

  See the Quabbin manual for a full description of the auto-point program.

• Set the integration time:

  ?NET TMAI 15 TREF 15 RPT 1

• Go the reference position, perform a calibration, then run the auto-point program:

  ?NET REF START CAL START APOI

• To view the pointing results look at screen 19:

  ?NET SCRE 19

5. Making the Map

• Set the name, co-ordinates and velocity of your source e.g.:

  ?NET MAIN NAME GGD12-15 EPOCH 1950.0 RA 060824.50 DEC -061112.0 VLSR 10

• Set your reference position:

  ?NET SAME REF RAMAP -10 DECMAP 20

• Select the correlator parameters and lines you wish to observe:

  ?NET IFTYPE 2
  ?NET START QTUNE
  ?NET CONF 1 COR LINE (13)CO-1 USB
  ?NET CONF 2 COR LINE 2 C(18)O-1 USB CONF 1

• Set the required bandwidth:
  ?NET CBAND 25

• Now you are ready to start your map

• Type "OTF" to view the otf-map parameters. A full desciption of the parameters can be found in the OTF manual.

  ?NET OTF

• Change the parameters by typing "PARA #" where PARA is the parameter name and # is the value you want to set for that parameter. E.g.

  ?NET KMAP 4

  for a map with RA as the scanning direction. The possible values for each parameter are listed in the OTF manual.

  You will need to set: KMAP, ROTANG, LX, LY, XOFF YOFF, DY, XRAMP, YRAMP, NBREF, NCAL, SKIP, TSAM and TREF.

  BX and BY should be set at 0.75 unless you really want to end up with a strange map, and DY should be set to 0.5 to ensure even sampling.

  e.g.

• Set your map size in arcmin:

  ?NET LX 10 LY 10

  and the offset of the map-centre in otf "footprints". I.e. divide the X (Y) offset in arcmin by LX (LY).

  ?NET XOFF 0 YOFF 0

  Remember X runs right to left for most co-ordinate systems so offsets to the right (west) of the "MAIN" position are negative.

• Set the integration time:

  ?NET TSAM 0.5 TREF 6 RPT 1

  The minimum required (optimum) integration time on the reference position is given by:

  TREF = SQRT(LX*NBREF/BX) * TSAM/2

  The factor of 2 at the end is because a reference is taken at the beginning and end of each scan.

• Start your map:

  ?NET START OTF

  The map program automatically carries out a calibration scan before starting the first integration.

  You can monitor the progress of your map in the top right hand corner of the terminal window, where the current scan number and total number of scans is given. This is only equal to the number of rows if NBREF = 1. (Remember this when setting "SKIP").

6. Finishing up

• At the end of your session you should "DROP" the telescope and stop it tracking:

  ?NET DROP

• Wait for the telescope to reach an elevation of 1.5 degrees, then type "HALT"

  ?NET HALT

• Remote observers should then "EXIT" the remote observing mode

  ?NET EXIT

  and close down the terminal emulation program by typing Ctrl-B followed by X.
  NEVER type exit if you are at the vt100 terminal in the control room, as you will exit the telescope control system!!

OTF Data reduction and analysis

Mark Heyer Last modified: Tue Apr 16 10:55:33 EDT 2002