Hello Roger,
Helmut and
Dialers,
From the first paragragh of Roger's
response:
"The error is reduced by about 20% using the
declination of 20 degrees rather than 23.44 as the base. I do not know why."
Why?
You mention that this is error is
summed...<insert math lingo here> for the total date table.
What declication gives the lowesr error at the equinox and solstice
dates?
Thanks,
Mike
36.9151 : -121.3539
36.9151 : -121.3539
----- Original Message -----
From: Roger Bailey <[EMAIL PROTECTED]>
To: Mike Deamicis-Roberts <[EMAIL PROTECTED]>;
Sonderegger Helmut <[EMAIL PROTECTED]>
Cc: <[email protected]>
Sent: Saturday, January 19, 2002 1:01
PM
Subject: RE: Seasonal Sunrise
Marker
>
> Following your suggestion, I checked further into the error in the seasonal
> marker. You are correct. There is a better date/declination to base it on
> than the solstice. There seems to be a minimum error at Declination = 20
> degrees. Have a look at the attached chart. The error is reduced by about
> 20% using the declination of 20 degrees rather than 23.44 as the base. I do
> not know why. The new curve of the error shows more but smaller humps. Sigma
> of 1.5 cm on the declination table of +/-156 cm is pretty close.
>
> This analysis is based on the calculating standard deviation, sigma. I
> calculated the position on the zodiac date line for the analemmatic dial and
> then the position calculated from the seasonal marker distances for various
> base declinations. I summed the square of the differences, divided by the
> number of points and took the square root. This example is based on the
> design for Mike Deamicis-Roberts at latitude 36.9. This error analysis is
> incomplete but it does confirm your suspicions.
>
> Mike, I recommend that you move the season marker on your dial out by 3.5
> cm, from 2.720 meters to 2.755 as this cuts the error by ~20%.
>
> The calculation for the season marker position is as given before but use
> declination of 20 degree to calculate the azimuth and the position on the
> zodiac table. Then solve for the season marker position based on the
> geometry of the triangle.
>
> Roger Bailey
> Walking Shadow Designs
> N 51 W 115
>
>
> ----- Original Message -----
> From: "Roger Bailey" <[EMAIL PROTECTED]>
> To: "Sonderegger Helmut" <[EMAIL PROTECTED]>
> Sent: Monday, January 14, 2002 5:14 AM
> Subject: RE: Seasonal Sunrise Marker
>
>
> > Hi Helmut,
> >
> > You make a good point here. Let me look at it and get back to you.
> Different
> > ways of looking at it give different results. This is the value of this
> > mailing list. It allows us to share ideas and develop better ones.
> >
> > Roger Bailey
>
>
>
>
