NavList:

I've been distracted by "other matters" and have failed to reply to some posts in the past few weeks. I'm trying to catch up... My target is ten posts today and tomorrow. Then I'll try to stay on top for as long as possible! :)

Gary L., you wrote:
"I purchased your app quite a while ago but I never got around to giving it a "go" until abour four months ago. Once a month I attend a meeting of the "Quiet Birdmen" professional aviators meetings in Ventura California which is right on the beach. So, recently, I have been taking some of my sextants with me each time and arrive early so as to take observation from the beach. You can "rap put" observations in quick sucession making it extremely easy to take many observations in just a few minutes. I don't even write down the information, I just leave my cellphone on to record my spoken readings of the time and sextant readings and do a "screenshot" of the information displayed on the app. You get virtually instant "feedback" on the accuracy of your sextant work!  Then, since you have recorded the information, you can use it to practice conventional sight reductions when you get home!"

Thank you. That's a great description. I rarely get feedback on apps so this is very helpful. The "instant feedback" in the app is, from my own perspective, the key benefit when we are in the trust the GPS mode (that is, when GPS Spoofing is not a concern).

I occasionally get inquiries from people new to celestial navigation who tell me about a trek they have made to the beach for practice sights, and they describe recording their work... taking the sight data home to work it up by tables, and then discovering that their sights are out by ten or fifteen miles. If only I could have explained about the app (or equivalent!) before the hours they spent doing this the long way... Of course many would-be navigators are attracted to celestial navigation because it is "tech-free", and I get that. It's a charming attraction and a challenge to do all this without tech. But, wow, it's so much more efficient to get over the hill of "beginner" issues using an app. And we can experience the joy, charm, and challenge after we get over that hill!

You added:
"The methodology you implemented is the same as that used by flight navigators by applying the usual "corrections" to the computed altitude, with the signs reversed, rather than waiting til after the observations to apply the "corrections" to "sextant altitudes."  Flight navigators use this technique since they need instant iresults."

Yes, and reading descriptions of these approaches from you and other NavList flight navigators were part of my inspiration years ago when I was building this app (hard to believe that was more than eight years ago).

Many surface navigators and navigation "authorities" (in sailing organizations, rule-making groups for sailing races, etc.) are more attached than ever to the explicit, specific rituals of traditional marine celestial navigation. Within just the past ten years, the focus on the ritualistic has increased significantly. Many of these true believers will assert that they are respecting traditions and time-proven systems, but they have no clue about the differences in concepts and practices found in celestial navigation up in the air. They're behaving like rule-driven robots. If it's not in the marine celestial rule book, then it's heresy! It's a shame since the differences highlight useful tools and modes of analysis and also emphasize the fundamental common ground that makes all celestial navigation work.

You concluded:
"On a different subject, several years ago you posted a method to accurately determine the index correction for your sextant with the use of a tripod and a more powrerful telescopy placed behind the sextant. I used your method that many years go to adjust the I.C. to zero on my Tamaya. Guess what, it has remained at "zero" ever since! How about rreposting that information for the new guys."

Great idea. I will try to do that this weekend. There are many topics that we have discussed in years past that deserve a fresh look. NavList content is often "ephemeral" (like "ephemeris data", it's valuable, forgotten tomorrow), and though the NavList discussion archives can answer many questions, fresh discussions are always, inevitably better ...until they're forgotten, the very next day. :)

Frank Reed