Last Update: 6th February 2017


Scan Tab

The "Scan Table" prescribes the movement of the 45-m telescope. The 45-m telescope can observe the object with 6 different scan patterns: single point, on-on, On-the-Fly, pointing, random and grid map. The "Scan Tab" helps you to make the Scan Table easily.

Scan Table

Enter your a name of Scan Table. Usually the name of your scan pattern. A configuration file will be saved under your working directory with the name of

	<the name of the Scan Table you defined>.scan

The limitations of file name of Scan Table are as folllows:

There are 6 different scan patterns to chose from. Select the scan pattern you intend to use from the pull down menu located at the upper right hand corner. The scan tab will switch to the corresponding scan pattern.

Single Point

"Single point" scan is a standard single point scan with a position switching method.

On Position

Off Position

You will be entering the off position here. This is usually set to an emission free region of the sky.

On-Off Sequence

Calibration

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On-On

The on-on mode is unique to the 2-beam receiver, and hence this mode must be used in conjunction with the TZ receiver. When the on-on mode is selected, one of the beams of the TZ receiver points to the source, while another beam points to the off position located 46" away from the source coordinates. When a single integration is done, then the telescope moves such that the 2nd beam is now pointed toward the on position. Thus, the user who is going to perform the On-On scan mode should previously know that the source is less extended than 46".

Most of the items here are described in the Single Point section. One important difference is that the user must specify the "Blank Sky Position for Intensity Calibration" instead of the off positions (which are automatically defined as 46" -- the beam separation of the TZ receiver -- , and rotate around the on position depending on LST and EL, and are located both sides of the on position). The centre position of emission free region should be used for the blank sky position as it is used for the absolute intensity calibration: The emission free region should cover both the TZ1 beam position and TZ2 beam position, which rotates around the TZ1 beam position.

On-On "Number of Sequences" is defined by usual on-source scan number of one beam. The total on-source scan number with two beams is double number entered here. The users should enter the value taking into account that On-On "Number of Sequences" in Obstable Z is half number of "Scan number for one ON-point" in the results of the observation time estimator. (The definition of outputted scan number in the observation time estimator will be modified after this observing period.)

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OTF

On-the-Fly mapping method is available for all receivers except for the TZ with two beam mode. Required parameters can be derived with Time Estimator for On-The-Fly Observations (also see A Guide to OTF Observations with 45-m).


Notes for OTF scan

Scan Pattern

A window to specify a scan pattern. Some symbols used below are as same as in Time Estimator for OTF.

Notes for the OTF observation with the FOREST receiver

Users must carefully make the Scan Table when observing with the FOREST receiver since the FOREST has the asymmetric beam alignment to the rotation centre of the dewar. An optical axis of the FOREST receiver is designed to be along the Beam 1. This changes the beam alignment due to a declination of a target. If users intend to observe an area of 2A[arcsec] x 2B[arcsec] with a position angle of 0 [degree], the parameters for the Scan Table should be as follows (Note that the position angle must be 0 for the OTF observation with the FOREST in the 2016-2017 observing season):

Declination > (+35d56m40s.17)? Initial Rotation Angle [deg.]* (dX0, dY0) Spacing, Nrow
Yes
0
(-A, -B)
Spacing x (Nrow-1) = 2B + BS**
Yes
+90
(-A, -B-BS**)
Spacing x (Nrow-1) = 2B + BS**
Yes
-90
(-A-BS**, -B)
Spacing x (Nrow-1) = 2B + BS**
No
0
(-A-BS**, -B-BS**)
Spacing x (Nrow-1) = 2B + BS**
No
+90
(-A-BS**, -B)
Spacing x (Nrow-1) = 2B + BS**
No
-90
(-A, -B-BS**)
Spacing x (Nrow-1) = 2B + BS**
*) "Initial Rotation Angle" should be input in the Device Table (not in the Scan Table). The rotation angle of the FOREST should be within +-100 degrees during one observing script.
**) Each beam separation (BS) of the FOREST receiver is 50 arcsec.

The following figures illustrate a mapping area with the beam alignment of the FOREST based on a declination of a target(> or < the latitude of the observatory[+35d56m40s.17]) and the Initial Rotation Angle (0, +90, and -90 deg.). The area overlapped with four beams is shown as a filled blue box.

Case 1: Decl. > +35d56m40s.17, Inital Rotation Angle = 0 deg.


Case 2: Decl. > +35d56m40s.17, Inital Rotation Angle = 90 deg.


Case 3: Decl. > +35d56m40s.17, Inital Rotation Angle = -90 deg.


Case 4: Decl. < +35d56m40s.17, Inital Rotation Angle = 0 deg.


Case 5: Decl. < +35d56m40s.17, Inital Rotation Angle = 90 deg.


Case 6: Decl. < +35d56m40s.17, Inital Rotation Angle = -90 deg.

After making observing scripts, please confirm that the observing region is as same as you intend to with ''obspoint.py''.

Off Point

Position(s) to obtain Off point(s).

Calibration

Parameters for R-Sky intensity calibration.

Scan Sequence

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Pointing

This mode allows the user to create an observing script for pointing (a 5-point cross scan). Many of the items here are common with the Single Point mode, and the user should consult the items discussed there. Some of the items listed in the "On Position", however, are unique to the Pointing mode, and are discussed in the following.

Generally saying, you just select and use a sample file from pushing the "Sample" button. Naming rules of sample files for the pointing observation are as follows:

	pt[frequency in GHz]_[integration time in seconds].scan

The observatory prepared 22 GHz, 43 GHz and 86 GHz sample files which correspond H2O maser, SiO(J = 1-0) maser and SiO(J = 2-1) maser, respectively. If your pointing source is too strong or weak to observe with default integration time, you just modify the integration time in "On Position" and "Calibration" section.

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Random

This scan mode should be selected when the user would like to observe multiple points in a single observation. The Single Point section may help you to make "random" scan table.

On Position

Off Position

On-Off Sequence and Calibration

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Grid Map

The "Grid Map" mode is designed to observe a rectangular area. Please note that in the "offset from center" mode at off position, the "start corner", and the "grid spacing", Obstable Z does not correct the factor of "cos(Dec)". Consequently, the offset position of the telescope moving in X coordinates (RA and L) shift from the position (X + dX) with the increasing the absolute value of Y coordinates (Dec and B).

On Position

Off Position

On-Off Sequence and Calibration

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Check for Basic Errors in Your Scan Table

Click the Check button for a basic check of the parameters. This feature only checks for simple typos and it is not meant for checking the details of the observational setup.

In order to check on-source positions according to your scan table, it is useful to utilise a tool named obspoint. This tool generates the positions of the on-source defined in your scan table.

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Save Your File

Click the Save button for saving the Scan Table. NOTE: This does not save the Observe Table. The user should click the Save button on the Files Tab for saving the main obstable script.

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