NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Venus During the day.
From: Paul Jackson
Date: 2010 Sep 12, 08:21 -0700
From: Paul Jackson
Date: 2010 Sep 12, 08:21 -0700
Hi Antoine, In answer to your question re Navigator software result ,yes you are right the software outputs 0.1 nautical miles toasted 048 .My original quote if I remember it correctly was "some of my intercepts have been down to 0.1 nm". I think Greg has pinpointed the area of confusion in asking me to clarify the dip to the horizon issue. The distance to the shore horizon was estimated in error by me.I stated the distance at 1.1 nm when in fact it is 1.8 nm , sorry about that. In answer to query #2 the coordinates you use cross check with the data on my plotting sheet. Query #5 I used an obscured horizon as you observed on google earth Rangitoto is in the way. And in answer to your last query,yes I was using a ASTRA III B Thank you so much for your interest in my shot of Venus. Best Regards Paul W Jackson. On Mon, 13 Sep 2010 01:05 NZST Antoine Couette wrote: >To the specific Attention of Paul W. Jackson, and Greg Redzinski : > >Dear Paul and Greg, > > > > >1 - Paul, in [NavList # 13785] you informed our NavList Community about your most recent "Venus daylight observations" taken in the "maritime suburb" of Auckland, Nouvelle Z�lande on Sep 09 th (local date). You subsequently published (Thanks again) one such observations under the form of a "picture" in your post [NavList # 13795] 11 Sep 01:31. > >Through carefully looking at your picture, I think that I can read the following note : "Result by Navigator = 0.1 NM towards 048�" > >And BTW, this note makes sense since this specific "0.1 NM" intercept seems to be the one you initially quoted in your very first post on this subject [NavList # 13785]. Am I right ? > >******* > >2 - In my post [NavList # 13808] 11 Sep 10:22, and because I had difficulties to read it, I "transcripted" your "pictured data" into plain typed figures so that everybody -yourself included- could check that this transcription is correct. Using these transcripted data, I then published an intercept of 1.2 NM Towards Venus, with an Azimut of 047�9. > >For the sake of being more comprehensive - so that anybody can crosscheck my computations - for the time of your observation I am using the following apparent coordinates for the Center of Light of Venus : > >GHA = 163�01'96 and >Dec = S -14�57'32 > >NOTE 1 : I compute the "Center of Light" apparent Coordinates of Venus from its "Geometrical Center" apparent Coordinates and by subsequently applying a correction of +0'153 to its GHA and of +0'069 to its Declination. > >NOTE 2 : Such apparent coordinates should both be accurate to better than 0.05'. > >******* > >3 - In your post [NavList # 13809] 11 Sep 2010 11:28, Greg you published an intercept value of "1.3 NM towards" through "using a natural horizon". Greg, did you use the same starting data as the ones I used in part 2 just hereabove ? >It would seem that yes, since our independently computed results are extremely close and their (subtle) difference certainly is not significant. I too was assuming "natural horizon" exactly as you did. > >******* > >4 - Then in your posts [NavList # 13814] 11 Sep 2010 01:47, and [NavList # 13815] 12 Sep 2010 02:38 Paul you kindly replied to each of us. > >******* > >5 - However, Paul, I still have one query rather similar to the unanswered query Greg asked you in 3 hereabove. > >How can we reconcile both our similar results ("1.2 NM towards" and "1.3 NM towards" intercepts ) with the "0.1 NM towards" intercept you seem to have achieved with "Navigator" ? It probably deals with the way of implementing the "dip" or "dip short" correction, whichever way you had to perform it. Actually, when looking on Google Earth, you were apparently quite close from getting a "obscured" horizon due to the western tip of Rangitoto Island. Which kind of horizon did you get ? obscured ? unobscured (= "natural" in the sense quoted hereabove)? > >Any additionnal clarification or further explanation from your side would be most welcome. > >One last question : were you not using an ASTRA III (B?) Sextant for this shot ? > >Thank you again, and > >Best Regards from > >Antoine > > >Antoine M. "Kermit" Cou�tte > > > >---------------------------------------------------------------- >NavList message boards and member settings: www.fer3.com/NavList >Members may optionally receive posts by email. >To cancel email delivery, send a message to NoMail[at]fer3.com >----------------------------------------------------------------