"Owen Duffy" wrote in message
...
"Jerry Martes" wrote in
news:cnwTi.7489$0l4.1447@trnddc08:

...
location and Az-El from your location, in real time. I have never
used the data to point my dish, but, if the data is erroroneous, Id
like to know where is wrong so it can be made better.

Jerry, I have no knowledge of the program you speak of, and cannot comment
on its accuracy.

Owen

Hi Owen

The APTDecoder program is written by Patrik Tast who lives in Finland.
The main reason for anyone using the program is to decode NOAA weather
satellite signals so images of the satellite's view of the Earth, from orbit
can be displayed on computers by amateurs (in real time).
I mentioned the "Flat Earth Monitor" in Patrik's program because it seems
to always be a source of Az-El and Lon-Lat for Sun and Moon position. You
tell the program where you are and the program tells you where to point. I
mentioned the "accuracy" because he is interested in knowing about any
improvements he can make to his program. Patrik does not charge for his
program. He is an amateur, interested in providing good data, and I
consider you to be a good critic.

Jerry

"Jerry Martes" wrote in
news:QFxTi.27907$DX.11271@trnddc06:

does not charge for his program. He is an amateur, interested in
providing good data, and I consider you to be a good critic.

Hi Jerry,

That is flattering, but undeserved I am sure.

There are a lot of calculators on the 'net for giving the Sun's position
at a place and time, and they use varying algorithms for more or less
accuracy.

The routines I used in the spreadsheet were unashamedly the work of some
one else, the chap who converted them to VBA and the original NOAA
javascript routines behind their page at
http://www.srrb.noaa.gov/highlights/sunrise/azel.html . I have accepted
they were good enough for my application, and they seemed quite close to
another navigator application that I have.

Owen

Owen Duffy wrote:
"Jerry Martes" wrote in
news:QFxTi.27907$DX.11271@trnddc06:


does not charge for his program. He is an amateur, interested in
providing good data, and I consider you to be a good critic.


Hi Jerry,

That is flattering, but undeserved I am sure.

There are a lot of calculators on the 'net for giving the Sun's position
at a place and time, and they use varying algorithms for more or less
accuracy.

The routines I used in the spreadsheet were unashamedly the work of some
one else, the chap who converted them to VBA and the original NOAA
javascript routines behind their page at
http://www.srrb.noaa.gov/highlights/sunrise/azel.html . I have accepted
they were good enough for my application, and they seemed quite close to
another navigator application that I have.



And, really, what precision do you need for pointing/plotting?

Presumably folks are looking at fairly wide beamwidths (so that the sun
size (1/2degree) is a small fraction of the beamwidth)
5 degrees?
1 degree?

Get into that 1 degree range and you need to start taking into account
stuff like the non-spherical earth, and stuff like the sun's apparent
diameter (which is different for radio and visible light, as well as
varying with the distance).

Heck, you might have to worry about whether your local gravity vector
(presumably what you used to set the elevation zero point) is
perpendicular to the geoid surface used for the look angle calculation.
And, whether your zero az is actually the same north as used in the look
calculation (as opposed to, say, aligned to Polaris at some arbitrary time)

(FWIW, the calculations behind the USNO page do take a lot of this stuff
into account)

Owen

Jim Lux wrote in
:

....
And, really, what precision do you need for pointing/plotting?

Presumably folks are looking at fairly wide beamwidths (so that the
sun size (1/2degree) is a small fraction of the beamwidth)
5 degrees?
1 degree?


Jim, I suggested in my article that the Sun technique was most suited for
beamwidths down to about 3 deg. As you have noted, there are a large
number of other factors that become relevant at small beamwidths, and the
most significant I think is the beamwidth correction factor to account
for the Sun's departure from being close to a point source, then as you
note the frequency dependent diameter of the radio Sun and the
distribution of the Sun's intensity.

So, down to 3 deg, the macros and formulae in my spreadsheet should be
more than adequate.

My thinking was that if you have a narrower antenna beamwidth, you
probably have sufficiently high G/T to use one of the radio stars which
will have much lower diameter.

Owen