# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: venus
From: Michael Dorl
Date: 2004 Oct 10, 21:02 -0500

```At 08:12 PM 10/10/04 +0100, George Huxtable wrote:

>Frank Reed's prediction, and mine, for Michael Dorl's recent Venus lunar
>show up an interesting discrepancy. We agree exactly on what the geocentric
>lunar distance ought to be, 17d  00.7', but when we calculate the
>near-limb-to-Venus angle, there's a difference. I get 16d 05.1'; Frank
>calculates 16d 05.5'. So there's a discrepancy of 0.4' between us,
>somewhere, in the process of allowing for semidiameter(s) and clearing the
>lunar distance. Not an enormous divergence, and certainly much smaller than
>the difference Michael Dorl observes with his measured distances. But
>clearing the distance and allowing for semidiameter should be a rather
>exact science, so I wonder why we disagree by that amount. It might be
>enlightening to track it down.

For whatever it's worth, my program using Mosier's routines gives a moon
center to venus center
refracted distance of 16d20m24.8s and a moon semi diameter of 15.065
minutes.  Thus a venus
center to moon near limb distance of 16d05m20.9s.  This assumes the time
was 11-13-06UT,
dt = 64.4, temperature 5C and pressure 1010.mb.  The program
gives  16d21'14.15"  for the
airless model.  I'd have to change my code to get the geocentric
distance.  Can do that tomorrow
if anyone cares.  The distance was calculated from topographic RA and DECL.

I'm now thinking my problem was in my observations.  Will try some with
stars and see if I can do better.

My main interest here was to determine if I had a problem with my program.

```
Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)