NavList:

Dear Brad,

Thank you for your detailed reply referenced on top of the list.

John D. Howard and Robert VanderPol II have since expressed their personal views. I am totally endorsing them and they seem comprehensive by themselves.

Most importantly and to make CelNav-DR a fully independent and last resort back-up of the back-ups, it is quite important to find ways of keeping accurate Time on-board for extended periods of time and at reasonable cost and in a practical way.

Hence the current conversations between yourself Brad, Robert VanderPol II, Francis Upchurch and others are extremely interesting in this respect.

May I suggest that the topic of "Maintaining self contained UTC on board" could be the title of a new series of dedicated posts devoted to accurately maintaining a sufficient Knowledge of UT1 onboard should UTC/UT1 broadcasting fail for some extended periods of time ? If you can keep onboard an affordable device which does not drift by more than 0.1 s / month relatively to UTC, that would be a wonderful tool. In this case CelNav/DR would be an extraordinary un-defeatable back up [of the backups] worldwide Navigation system. Such very stable UTC clock should give more than adequate time to rejoin a known spot and update it through a Celnav Fix from a known position. Food for thought to many Members here ...

Let us not forget either that Lunars can derive UT to +/- 30 seconds of time under normal conditions. This is far from being mirific but knowing one's Longitude to +/- 8' still makes landfall a reasonable exercise provided your exercise sufficient caution and judgement.

A last and non-essential point - far from being a rationale per se - is that [hand-held] electronic personal devices make CelNav much more "fun" than it used to be. This has also been pointed out by Hewitt Schlereth in "Susceptibility-GPS-CME-Rationale-for-CN-Schlereth-oct-2018-g42957", by Francis upchurch in "Susceptibility-GPS-CME-Rationale-for-CN-Upchurch-oct-2018-g42961" . Nonetheless should such electronic tools fail, it is a must to be able to tackle CelNav with tables, paper and pencil, and even starfinder. Many different "manual" methods are available as parts of "Emergency Celnav toolkits" earlier descriptions in NavList posts. Greg Rudzinski and others are extraordinary wizards in this area.

Dear Brad, I fully trust that my lateral thinking reply is not exactly up to your strong expectations. Unlike "planet phase correction" or others subjects, this current topic is not a scientific one.

It can and should accept multiple answers. Would you not agree now ?

Very Best Regards,

Antoine M. "Kermit" Couëtte