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ZL3AI > APRDIG 19.03.04 13:30l 250 Lines 9104 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: Transit of Venus on APRS
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Mon, 15 Mar 2004 18:27:48 -0500
X-Message-Number: 19
>Yes, exactly. You draw a 2.53" or 2.53cm circle on the
>graph paper and whenever you want to enter a posit,
>simply move the telescope to re-center the sun in the
>circle. [then read Venus's position off your grid and enter
it into APRS]...
Actually, the only reason for that size is so that you can
use existing ruled graph paper. If your telescope projects
a much larger image, then you can use multiples of that
size. The bottom line is that you want the sun to be
able to be projected onto X-Y lined graph which is exactly
2.55 somethings in radius.
The SUN object in APRS that we will use as the big yellow
circle is as follows:
SUN>APRS:!0000.01N/00000.01W15081408
Please plot this in your favorite APRS program and verify
that it plots as a 2.55 minute radius yellow circle. If not
then we have different clients doing objects differently and
need to resolve that first.
Let me know so we can decide what to do next...
de Wb4APR,Bob
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Subject: Re: Transit of Venus on APRS
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Mon, 15 Mar 2004 18:32:57 -0500
X-Message-Number: 20
>I must be doing something wrong.
>Every time I try this, my graph paper
>bursts into flames. ;)
Probably a joke, but yes, if you focus all the suns rays to a point, the
point burns. If howver, you focus the sun to an image, then the image is
not a focus of sun's rays but a divergence, thus it is dimmer and less heat
than the sun was in the first place.
Thus it is cool, and it must be viewed in relative dark or a shadow, or you
canot see the projection... because of the bright sunlight all around it...
Bob
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Subject: Re: Transit of Venus on APRS
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Mon, 15 Mar 2004 18:41:03 -0500
X-Message-Number: 21
>Probably a joke, but yes, if you focus all
>the suns rays to a point, the point burns.
>If howver, you focus the sun to an image,
>then the image is not a focus of sun's rays
>but a divergence, thus it is dimmer and
>less heat than the sun was in the first place.
I always thought that the 'best you could get' for focus was the picture of
the sun on the paper, and all else was 'divergence' and 'fuzzy'. And that
the focus of the sun was what made it hot enough...
Maybe I wasn't 'focused enough' to a point, but I remember one time when I
was burning ants on the sidewalk (hey, I was a little kid, ok?) suddenly
being amazed at seeing an image of tree that was overhead off to the side
on the sidewalk too.
You're saying that's not the case?
Mike
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Subject: Re: Transit of Venus on APRS
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 15 Mar 2004 15:52:30 -0800
X-Message-Number: 22
>Probably a joke, but yes, if you focus all
>the suns rays to a point, the point burns.
Yeah, it was a joke. =] I would like to get ahold of one of those huge
fresnel lenses, though. One square meter should be about a kilowatt of
power, concentrated on a very small area.
>Thus it is cool, and it must be viewed in
>relative dark or a shadow, or you canot
>see the projection... because of the
>bright sunlight all around it...
I could swear that somewhere I saw a camera obscura style solar telescope
thing on display. I don't know where that might have been. I checked
Google, and it looks like Kepler used something like that to observe the
1606 transit of Mercury.
Are any observatories going to carry the event on the web? Will SOHO be
able to see it?
Scott
N1VG
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Subject: Re: Transit of Venus on APRS
From: "Scott Miller" <scott@opentrac.org>
Date: Mon, 15 Mar 2004 15:58:24 -0800
X-Message-Number: 23
>Are any observatories going to carry the event on the web? Will SOHO be
>able to see it?
Never mind, found this at
http://sohowww.nascom.nasa.gov/operations/SPWG/spwg-20040227.html..
SOHO will see Venus at closest approach to the solar centre on June 8th,
2004 at 13:40 UTC (to 1 minute precision and with 5.7 minutes light-time
delay taken into account). The angle of Venus-Sun separation at that epoch
will be 0.31741194 deg (1142.68 arc-sec). By comparison, the solar angular
radius as seen from SOHO will be 0.2648485 deg (953.45 arc-sec), and the
angular diameter of Venus will be 59.5 arc-sec. At the point of epoch of
closest approach, the Venus position angles (measured counter-clockwise
around Sun from reference) will be 171.5 deg (from North Ecliptic Pole) and
178.75 deg (from Sun's North Pole). Note that SOHO sees the transit event
about 5.3 hours after Earth does.
We will be making a 5-minute ephemeris available shortly, together with IDL
tools similar to what was provided for the 2003 Mercury transit. The
ephemeris will be updated after next S/K manoeuvre.
Other relevant information (the transit as seen from Earth) can be found at
http://sunearth.gsfc.nasa.gov/eclipse/OH/transit04.html.
We would like to know from instrumenters how far out (i.e. solar radii) the
ephemeris needs to go.
The Venus transit will be observed by SUMER, CDS, EIT, UVCS and LASCO. We
will be in Submode 5 during the Venus transit.
TRACE will also observe the Venus Transit.
LASCO will do special observations with ground based observatories from
about June 3 to June 13. In Submode 5, this will mean a roughly 2-hour hole
in EIT's CME watch those days.
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Subject: Re: Transit of Venus on APRS
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Mon, 15 Mar 2004 19:27:32 -0500
X-Message-Number: 24
>I always thought that the 'best you could get' for
>focus was the picture of the sun on the paper,
>and all else was 'divergence' and 'fuzzy'. And
>that the focus of the sun was what made it
>hot enough...
Yes, you are right and I confused things. That is a one lens projection,
making the image of the sun very small (and threrefor hot). What we are
looking for is a magnified projection of the sun over a larger area (for
resolution) and that then is cool. But it takes two lenses to get a
magnified image..
Bob
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Subject: Re: Transit of Venus on APRS
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Mon, 15 Mar 2004 19:38:00 -0500
X-Message-Number: 25
>>>"Scott Miller" said:
>I could swear that somewhere I saw a camera obscura
>style solar telescope thing on display. ... I checked
>Google, and it looks like Kepler used something like
>that to observe the 1606 transit of Mercury.
Yes, I initially wanted to do the camera obscura thing but it only projects
a 1 for 1 image, meaning that the 0.5 degree sun will project a 0.5 degree
image.
THus you can get any size, it just depends on how far away you put the
screen. But to get a 5" size, then you would need to be about 500 inches
away or about 40 feet. And the image would be so dim, we would need total
darkness to even see it.
THe dimness is easy to realize, because the only light you have is what
comes through the pin-hole and yet it has to light up a 25 sq inch image 40
feet away...
Then you have to move the room over 90 degrees as the sun moves during the
6 hours of the event...
So I soon abandoned that idea... :-(
Bob
..
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Subject: OpenTracker update
From: <scott@opentrac.org>
Date: Mon, 15 Mar 2004 17:32:43 -0800
X-Message-Number: 26
The OpenTracker finally has a Windows-based configuration program. It's
still in beta testing, but it's mostly operational. It only mangles your
configuration once in awhile. =] The firmware load is super easy now, and
will soon allow you to pick from a menu of available firmware images
downloaded from the web in real time.
There's a screenshot at http://n1vg.net/opentracker/images/conftest.gif.
Note the new configuration switch options in the lower left corner. I think
a lot of people (balloon flyers especially) should find these useful. Keep
in mind that the settings are independent for each configuration. In this
screenshot, you can see that Config 1 is set to switch when the speed's
greater than 100 Km/h AND the jumper is on. You can't see it in the
screenshot, but Config 2 is set to switch back when the jumper is removed OR
the speed drops below 60 Km/h.
The point is that the conditions don't need to be related. Of course, that
means that both can be true at the same time, which would result in the
tracker switching configurations once a second. Which I guess might be
useful if you want to randomize things a bit.
[commercial content deleted]
http://n1vg.net/opentracker
Scott
N1VG
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