PROTECTED] On
Behalf Of Dr Bruce Griffiths
Sent: 29 September 2006 01:09
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Re Danjon Astrolabe
Tom Van Baak wrote:
The scheme probably needs three photocells to be sure that the one
in the middle
.
Robert G8RPI.
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Dr Bruce Griffiths
Sent: 29 September 2006 01:09
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Re Danjon Astrolabe
Tom Van Baak wrote
and frequency measurement
Subject: Re: [time-nuts] Re Danjon Astrolabe
Tom Van Baak wrote:
The scheme probably needs three photocells to be sure that the one
in the middle is darker than the others. Might be able to mask it
with a slit and use a fine wire gnomon, in a coarse/fine servo.
Could use
At 09:22 AM 9/29/2006 , buehl wrote:
the fiber. I have had good results attaching one end of cheap plastic
fiber to tip of photodiode with clear glue or epoxy. Cheap plastic fiber
like that used in decorative lamps, or experimentor type sold by Radio
Shack, will also pass IR for short
Accuracy still won't be much better than1% of the solar diameter or
about 1 second of time nowhere near the o.1 sec or better hoped for.
Bruce
Bruce,
Can you show us how to derive the accuracy number?
I would have guessed that with fractional degree Al-El
steering, a rotary encoder, 12
Hi,
About transits - I like the bit in the film Longitude (if I
remember it correctly) were Harrison's son is asked by some worthy
how they get a local time check. The young lad points to the
chimney on a certain house and says that they wait for a
particular star to disappear behind it.
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
Here's a related idea for you; a modern digital sundial.
Two different ways to implement it:
1) Aim a webcam on a standard sundial and write some
image processing software that
Hi Tom:
With an atomic quality clock it should be possible to measure the period
of the earth every day using the sun and/or stars and see how far from
86400 seconds it is.
I too have been thinking of how to use the sun in a precision way.
Since UTC is close (UTC1 is better) to the sun's
Tom Van Baak wrote,
2) Instead of a fixed base, gnomon, and slowly moving shadow like
almost all sundials, you put a stepper or servo motor/encoder on the
base. Then place matched photodiodes on either side of the gnomon and
steer the whole sundial for constant *minimum* shadow. In real-time, a
I wrote,
The scheme probably needs three photocells to be sure that
the one in the middle is darker than the others. Might be
able to mask it with a slit and use a fine wire gnomon, in
a coarse/fine servo. Could use a variable frequency motor
and precision reduction, like a phonograph turntable
Dr Bruce Griffiths wrote:
David Forbes wrote:
Bill Hawkins wrote:
Tom Van Baak wrote,
2) Instead of a fixed base, gnomon, and slowly moving shadow like
almost all sundials, you put a stepper or servo motor/encoder on the
base. Then place matched photodiodes on either side of
The scheme probably needs three photocells to be sure that the one
in the middle is darker than the others. Might be able to mask it
with a slit and use a fine wire gnomon, in a coarse/fine servo.
Could use a variable frequency motor and precision reduction, like
a phonograph turntable only
Tom Van Baak wrote:
The scheme probably needs three photocells to be sure that the one
in the middle is darker than the others. Might be able to mask it
with a slit and use a fine wire gnomon, in a coarse/fine servo.
Could use a variable frequency motor and precision reduction, like
a
I wonder if it is possible to use radio astronomy. You'd have to find
an object that doesn't require a very large antenna to acquire its
signal.
I understand that optical tracking of a star crossing a hair is more
precise than the peak of a radio signal, but perhaps modern signal
Brooke Clarke wrote:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
This sounds like an interesting project. I've been looking for something
to do with the Meade 4455D telescope I just got. (D=114m F=910, f/8)
Doing a
Glenn wrote:
Brooke Clarke wrote:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
This sounds like an interesting project. I've been looking for something
to do with the Meade 4455D telescope I just got.
Glenn wrote:
Brooke Clarke wrote:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
This sounds like an interesting project. I've been looking for something
to do with the Meade 4455D telescope I just got.
Hi Bruce:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
There are automatic star trackers that can see stars in the day time
so the only time you would not see the star is when there's cloud cover.
By using a reticule it
] [mailto:[EMAIL PROTECTED] On
Behalf Of Brooke Clarke
Sent: Tuesday, September 26, 2006 12:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Re Danjon Astrolabe
Hi Bruce:
I'm interested in automatically measuring the earth's period by looking
close to straight
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