NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Additional altitude correction for Venus
From: Stan K
Date: 2015 May 15, 10:43 -0400
From: Stan K
Date: 2015 May 15, 10:43 -0400
Catherine Hohenkerk came through again. The change occurred in 1985. The relevant part of her response is below.
Stan
-----Original Message-----
From: Hohenkerk Catherine <Catherine.Hohenkerk@UKHO.gov.uk>
To: 'slk1000@aol.com' <slk1000@aol.com>
Cc: hmnao <hmnao@UKHO.gov.uk>
Sent: Fri, May 15, 2015 8:33 am
Subject: RE: [NavList] Re: Additional altitude correction for Venus - RESOLVED
From: Hohenkerk Catherine <Catherine.Hohenkerk@UKHO.gov.uk>
To: 'slk1000@aol.com' <slk1000@aol.com>
Cc: hmnao <hmnao@UKHO.gov.uk>
Sent: Fri, May 15, 2015 8:33 am
Subject: RE: [NavList] Re: Additional altitude correction for Venus - RESOLVED
Dear Stan,
Thank you for your e-mails. I was preparing an answer, but you have half answered it!
I do agree that in older NAs its not very clear! This is what I wrote yesterday …
In the 1980's it was decided that in The Nautical Almanac (NA), for Venus, the
tabulated values of GHA and Dec should be changed from the centre of the disc
to the centre of light (i.e. to take account of the phase), since this is what
the observers would be measuring their altitudes from. The effect of the change
changed the additional corrections tabulated on page A2 and the wording in the
explanation (usually near the bottom of page 259).
This change was implemented in 1985. Looking on page 259 of
the NA for 1985, it states in the penultimate paragraph:
"Since 1985, the phase correction for Venus has been incorporated in the
tabulations for the G.H.A. and Dec., and no correction for phase is required."
Catherine
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
HM Nautical Almanac Office
United Kingdom Hydrographic Office
Admiralty Way
Taunton TA1 2DN
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
