Last Update: 25th December 2018
The Reference table is a newly-introduced table, which describes how to subtract noises from atmosphere and instruments. When we observe any target, a receiver outputs a summation of power throughout the path from the line-of-sight: the emission of the target and noises from the atmosphere and instruments including the radio telescope itself. In order to derive the emission of the target, there are two ways to subtraction of the noise. One is a position-switch method, the other is a frequency-switch method. For the 2018-2019 observing season, a frequency-switch method is NOT implemented on the nobs.
This field defines a name for the reference table. The file will be saved in your working directory, which is as same as 'Project' you entered at the Project tab. For example, your account ID, project name, and a name of the reference table are 'newobs', 'proj1', and 'ref1', respectively, your file is saved in
with a name of 'ref1.nreference'.
As other tables, a filename should follow the rules described below:
NOTE: You can save the input parameters anytime you want (the nobs allows you to save the reference table even if some mandatory fields still blank). The nobs does not check whether these input parameters follow the rules at that time.
You can use this space to write any note about the reference table. A character limit is 100, and a line break is prohibited.
It is needed to observe blank-sky (i.e., an emission-free region of the sky) that is close to the target, whose condition can be regarded as same as the atmosphere at the target, and subtract the blank-sky data from the target data. This position of the 'blank-sky' is called as an 'off-position'. Current nobs implement only 'position-switch' mode.
Choose a method to specify the off-positions from 'Absolute position' and 'Offset from the source position'.
With this type, you can directly specify the off-position in the coordinate system, which you choose at 'Coordinate System'. This position type would be effective when no bright source at the frequency you intend to observe are expected around the target (For example, along with the Galactic plane).
The off-position will be defined as a position from the target which is defined in the source table. This position type is useful especially for extragalactic sources, around which no emission and absorption is expected.
Choose the coordinate system from 'Equatorial (J2000)', 'Equatorial (B1950)', 'Galactic', and 'Horizontal'.
9 off-positions can be stored at maximum.
1. You must choose the same coordinate system specified in the source table.
2. In case of using 'On-On' or 'Cross Point' in the scan table, the nobs automatically adopts the off-position written in (1) fields.
When you choose 'Equatorial (J2000)' or 'Equatorial (B1950)', off-positions are described in (α, δ) coordinate system.
If 'Galactic' is chosen in 'Coordinate System', off-positions are regarded as written in (l, b) coordinate system.
Specification off-positions in (Az, El) coordinate system is available when 'Horizontal' is selected in 'Coordinate System'.
If you choose 'Offset from the source position' in 'Position Type' field, an off-positions should be written as offset from the source position, which you define in the source table.
For a pointing observation with a SiO maser (both for 43 GHz and 86 GHz), we recommend to use the following parameters:
If you observe H2O maser at 22 GHz for checking pointing accuracy, the same parameters are recommended except for 'Offset dx' of '0 3 0' but '0 6 0'.