The MERLIN User Guide

The 2003 version of the MERLIN User Guide is available and is the current edition. Please let us know about any omissions, errors or things which are not clear.

Online MERLIN User Guide

Postscript (gzipped) MERLIN User Guide
PDF of MERLIN User Guide

Initial processing of raw MERLIN data (`dfiles') and conversion to FITS must be done at Jodrell Bank using local `d-programs'. For local users see the tdproc help file (you must be on a JBO Sun machine).

All further data reduction can be done in AIPS and other commonly available packages. The MERLIN User Guide describes the whole process in detail.
Recentnotes.txt describes any current peculiarities or bugs not documented in the MUG:

  1. Jun 2003 Single-baseline documentation error
  2. Aug 2003 tdproc for spec. line data - select odd No. chans
  3. Aug 2003 Enhanced sensitivity/frequency range at C-band (obsolete)
  4. Oct 2003 Cross polarisation bandpass slope - delay error
  5. Aug 2004 VLA coordinate conversion
  6. Mar 2006 For methanol or other 6 GHz data with >2 antennas use normal processing
  7. Jun 2006 Coordinate conversion in AIPS and FLATN
  8. Jun 2006 updated Jun 07 Sensitivities and weights at 5-7 GHz

There is a separate page for proposal information

The MERLIN Archive contains partly processed continuum data (visibilities and images) which can be downloaded by ftp or supplied on tape. It also contains some flux density measurements of calibration sources, or see below:

Position accuracy

The factors affecting position accuracy are described in the MERLIN Guide. The positions of phase reference sources are found in these catalogues (see the MERLIN User Guide Appendix A for more catalogues, most of which are available on-line via ADS or Vizier). Alternatively, use Vizier to find the most recent published position of a source.

VLBA calibrator list and the VCS1 survey (Beasley et al. 2002).

2-cm Survey

Jodrell Bank/Caltech surveys

USNO Radio Reference Frame Image Database which also provides links to other surveys.

VLA calibrator list and flux densities

NOTE
Please include appropriate references in publications in recongnition of the hard work which has gone into these surveys.
Even reference sources are likely to show different structure on different scales/frequencies and may be variable.

Note that the positions used for older observations may differ from the most recent catalogues, and the MERLIN data can be shifted accordingly if required.

Tsys measurements

Recent MERLIN antenna Tsys measurments. Note that older data (e.g. 1992-2001) are likely to have higher Tsys values.

Flux density calibration

Table of flux densities of MERLIN point calibrator sources at L- and C-band (OQ208, 0552+398, 2134+004, 3C84, 3C273). At these frequencies the flux densities are found by comparison with 3C286 (using the shortest MERLIN baselines). The flux of 3C286 can be found from Baars et al. (1977) or by typing
    % dflux
on a Sun workstation at JBO.

At 6 GHz, at the present time (Jul 2002) the flux of the calibration source 3C84 is not well-known and is assumed to be 10-15 Jy in recent years.
At 22 GHz, calibrator source fluxes are obtained from monitoring at the Metsahovi observatory; please consult MERLIN staff for the appropriate value (this is to ensure appropriate acknowledgement of unpublished data).

Flux scale improvement
The flux densities of the common calibrator sources in the table above are generally good to 10% for the fainter sources and to 50% for the bright sources used for high-spectral-resolution bandpass calibration. If you use an estimate (AFLUX for 'dcal' in `tdproc') you can improve the flux density calibration in AIPS by using a small runfile after loading the data.

To calculate the flux density of a point calibrator source using d-programs, see the Merlin User Guide Section 5.1. You can perform the calculation in Section 5.1.6 with a small Fortran program flux.f which you can copy and compile. Sensitivities and weights at 5-7 GHz gives C-band Tsys values for 2004-2007

Local data reduction pipelines and other utilities

Link to descriptions of automatic data reduction scripts.