I found this just by chance, so perhaps not all are aware of it:
http://www.ras.org.uk/news-and-press/2641-new-version-if-the-mnras-latex-package
<QUOTE>
New version of the MNRAS LaTeX package
Last Updated on Friday, 29 May 2015 16:50
Published on Friday, 29 May 2015 16:44
MNRAS coverThe journal Monthly Notices of the Royal Astronomical Society
(MNRAS) encourages authors to prepare their papers using the LaTeX
document preparation software. MNRAS provides a LaTeX package (called
'mnras') which allows authors to approximate the final appearance of the
journal. It includes numerous features to simplify the preparation of
papers.
MNRAS has just completed a major update to this package, version 3.0,
which includes:
* Additonal functionality, including links and a new \ion command
* Improvements to page layout, positioning of figures etc.
* Updated appearance to be closer to the final journal
* Better BibTeX support, including automatic treament of arxiv
preprints, three-author papers and journal shortcuts used by NASA ADS
* Completely rewritten documentation
* A new template to ease writing a new paper
Authors are encouraged to use the new package and updated style files.
It can be downloaded from this directory at the Comprehensive TeX
Archive Network (CTAN).
</QUOTE>
The CTAN link is
http://www.tex.ac.uk/tex-archive/macros/latex/contrib/mnras/ .