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On Mon, 6 Dec 2004, Frank Reed wrote:

> I can get lunars
> accurate to 0.2 to 0.3 minutes on a regular basis

I also can sometimes:-) But unfortunately not on the "regular basis".

> Alex wrote:
>> "My conclusion is that I am reasonably confident in 1'
>>  accuracy (of the
>>  distance) but not much better.
>>  Some of my lunars are 0.6 and  even 0.7 off."

> But those occur under specific circumstances, right?
> Large angles, and
> always positive error, right?

Always positive, but sometimes 0.1, sometimes 0.3 and sometimes,
unfortunately, 0.6. It is always a "systematic error",
I mean that the variation of the error in a series of 5-10
distances are small (about 0.2).

> This
> should be telling you something.

That's why I am discussing refraction, irradiation and collimation
all the time:-)

> Or, accept it as an error of unknown
> origin and subtract that amount as an instrument error

It does not ALWAYS occur. I already posted some nearly perfect
lunars, and have more.

> Or, avoid those angles! As noted above,
> navigators limited themselves
> to  certain angular ranges in the great majority of cases.

Well, I do not do this for my living:-) Why should I avoid angles?
I do just the opposite: try to measure angles as large as possible.

Alex.

   

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