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frankreed@HistoricalAtlas.net wrote:
 > And you added:
> "FWIW, I used NVDs in the cockpit back in the 1980s and 1990s."
>
> Just to clarify, when you personally were doing this, did you get your
> percent ilumination data directly from the Nautical Almanac?? Surely, it

Frank,
Yes it was gotten from the NA but published on a daily flight schedule
so that all pilots knew what the percent moon illumination was and
whether or not NVD's could be used if you were flying that night.

> wouldn't be left to each aviatot to dig out the NA just to read off that one
> number, right? I would think that this would be something that would be
> announced on the day of operations, e.g. "tonight the waning Moon is too
> bright, no NVDs after 2030 hours". And it's the sort of thing that only

No it wasn't left to each pilot to look it up but all pilots were
responsible for knowing the flight schedule for the next day and the
flight schedule writer dug it out of the NA and published it via the
daily flight schedule.

> needs to be tabulated in one short table --the sort of thing you could stick
> on a single index card-- for the entire year.

True you could.  But why go to the extra tabulation work when all the
schedule writer had to do was look it up in the NA.

> And you wrote:
> "Of course, there may be other uses for percent moon illumination, I just
> know what I used it for 10-20 years ago and is still used today wherever
> NVDs and flying at night from a ship come together."
>
> It strikes me as a bit of a roundabout solution for a simple problem. Why
> not just stick a light sensor on the NVD? If the Moon's too bright (or the
> aurorae for something else that could cause the same problem), it beeps at
> you.

I can only speak to the NVDs I have used and unfortunately we didn't
have a light sensor attached to it to bitch at us.  Well, we could have
easily just put the NVDs on walked outside and if it was too bright just
taken them off, an even easier solution.  It had to do with established
regulations for when we could use them since pilots and aircrew had died
in flight related accidents using NVDs when there was too much moon
illumination, so call it a safety factor.

> And you wrote:
> "As to the value of percent illumination to lunars or celnav... well, if
> you hooked up a 5th generation NVD to a sextant... there actually might
> be some nights when you couldn't effectively use the Sextant/NVD
> combination."
>
> Ok, you've got me thinking. For sight planning, using a standard sextant (no
> NVD), I could imagine a well-prepared navigator who has carefully determined
> the exact combination of shades required for every level of the Moon's
> illumination. Of course, the Moon's age in days would seem to fit the same
> bill (approximately, not quite the same), and that was in the modern NA from
> the beginning.

> Scott, you concluded:
> "I am sure that Lu thinks this explanation is BS too.  He is of course
> entitled to his opinion."
>
> For what it's worth, I personally didn't see anything particularly negative
> in his posts. I didn't see any point where he implied that your comments
> were "BS". I do understand why you took exception to his suggestion that you
> had "assumed" something, and you correctly corrected that. Of course, my
> comments here are merely MY opinion.  :-)
>
>  -FER
You are correct. My issue was with Lu claiming that I had "assumed"
something when I did not.  I probably did not explain it well initially
so this may have led Lu to think that I assumed something I did not.

--Scott

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