NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Santa Barbara 2016: Venus sight
From: Bill Ritchie
Date: 2017 Jan 2, 14:40 -0800
From: Bill Ritchie
Date: 2017 Jan 2, 14:40 -0800
May I bump into this thread as a new poster and developer of the Excel spreadsheet (Astron) that Peter used and attached?
I agree that, with sextant altitude sights of planets, it is customary to 'split' the horizon, However the spreadsheet allows the user to decide whether to specify body center or upper or lower limb. In the subject case, I see that Peter has selected the upper limb and the SD was subtracted. The USNO data always seems to use the lower limb and adds the SD. In the case of a crescent Venus, the apparent centre is none of these - as Frank Reed excellently explains on this forum "Apparent position of Venus corrected for phase" 2012 Sep 30, 11:30 -0700.
Bill Ritchie
