Re: What's the inner scale on this photo for?

2021-10-29 Thread Bill Gottesman
Or the slot near one end of the adelaide is just to guide the adelaide as
it slides back and forth in the internal geared mechanism.
Clearly a vertical gnomon had to be present on some part of the adelaide.
I think Steve is on the right track.
In terms of the screws or pins blocking movement of the adelaide, I think
the whole center section (curcular brass plates) pivots along with the
adelaide, so that is moot.

-Bill again.

On Fri, Oct 29, 2021 at 9:24 PM Bill Gottesman 
wrote:

> My two cents:
> I have a different guess about the round dial with the indicator.  My
> guess is that it is a calendar of months, and that turning the indicator to
> the correct month adjusts the length of the adelaide to the correct
> distance for reading time on the azimuth dial.  I do not know what casts
> the shadow, but I will guess that Sara is correct, that the slot holds a
> vertical vane.
>
> Being an azimuth dial, the correct declination scale must be used.  I see
> the circular declination lines, but they are not named.  So I think the
> pointer of the adelaide is set to the correct circle radius (correct
> length) by turning the indicator.
>
> -Bill
>
> On Fri, Oct 29, 2021 at 6:04 PM Steve Lelievre <
> steve.lelievre.can...@gmail.com> wrote:
>
>> Thank you, Sara and Patrick for your replies to my question.
>>
>> I shall try to get to the Science Museum sometime to have a look at the
>> dial, if that can be arranged.
>>
>> I’ve been trying to figure out how the cam that Sara mentioned might work.
>>
>> I’ve never studied the working of cams and this case isn’t obvious to me
>> as there are two inputs, azimuth and declination, that must drive the
>> minutes shown.
>>
>> If anyone can send me an explanation or drawing, it would me much
>> appreciated.
>>
>> Steve
>>
>> On Mon, Oct 25, 2021 at 19:19, Schechner, Sara 
>> wrote:
>>
>>> Hi Steve,
>>> The photo of the azimuth dial is hard to read.  I don't know what screws
>>> you are talking about preventing the arm from turning.  The arm is
>>> backwards at the moment since the pointed end should be on the scale of
>>> hour lines.  I am not convinced that there is a flap on the square end of
>>> the arm for a vane.  The sun at most angles would not fall far along the
>>> arm to reach the other end where the slot is.  Rather, I suspect there was
>>> a vertical gnomon in the slot at the pointed end.  Its shadow could have
>>> been aligned with the point so that the point was in line with the sun's
>>> azimuth.  As for the round dial, it almost always shows minutes and is
>>> geared to the rotation of the arm.
>>>
>>> That's my best guess.
>>> Sara
>>>
>>> -Original Message-
>>> From: sundial  On Behalf Of Steve Lelievre
>>> Sent: Monday, October 25, 2021 1:22 PM
>>> To: Sundial List 
>>> Subject: What's the inner scale on this photo for?
>>>
>>> Hi,
>>>
>>> Today a website called Vermont Free Press published an appallingly
>>> confusing (to me) summary of types of sundials. If you can bear to look,
>>> it's at https://www.vermontpressbureau.com/types-of-sundials/
>>>
>>> However, there was one thing about it that piqued my interest: the photo
>>> of an azimuth sundial (
>>> https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg
>>> ).
>>>
>>>  From what I can make out, there is a metal flap at the end of the
>>> alidade / sighting arm (the end at top in the photo). It must get turned up
>>> to make a shadow-caster.  I guess the arm has to be rotated so that the
>>> shadow falls along it, and time is then read from where the right-hand edge
>>> of the arm crosses the net of hour and declination lines. But then,
>>> wouldn't the screws seen in the upper plate block the arm from being turned
>>> to the required orientation?
>>>
>>> Another bit I can't figure is the little circular scale just north of
>>> the centre of the dial, with the pointer. Perhaps just an Equation of Time
>>> scale? Or perhaps a cam connects it to the arm so that it can be used to
>>> set the arm's length? (The slot in the arm suggests it can be slid in and
>>> out to set the tip at the applicable declination circle, which is a nifty
>>> feature.)
>>>
>>> Cheers,
>>>
>>> Steve
>>>
>>> ---
>>> https://lists.uni-koeln.de/mailman/listinfo/sundial
>>>
>>> --
>> Cell +1 778 837 5771
>> ---
>> https://lists.uni-koeln.de/mailman/listinfo/sundial
>>
>>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



Re: What's the inner scale on this photo for?

2021-10-29 Thread Bill Gottesman
My two cents:
I have a different guess about the round dial with the indicator.  My guess
is that it is a calendar of months, and that turning the indicator to the
correct month adjusts the length of the adelaide to the correct distance
for reading time on the azimuth dial.  I do not know what casts the shadow,
but I will guess that Sara is correct, that the slot holds a vertical vane.

Being an azimuth dial, the correct declination scale must be used.  I see
the circular declination lines, but they are not named.  So I think the
pointer of the adelaide is set to the correct circle radius (correct
length) by turning the indicator.

-Bill

On Fri, Oct 29, 2021 at 6:04 PM Steve Lelievre <
steve.lelievre.can...@gmail.com> wrote:

> Thank you, Sara and Patrick for your replies to my question.
>
> I shall try to get to the Science Museum sometime to have a look at the
> dial, if that can be arranged.
>
> I’ve been trying to figure out how the cam that Sara mentioned might work.
>
> I’ve never studied the working of cams and this case isn’t obvious to me
> as there are two inputs, azimuth and declination, that must drive the
> minutes shown.
>
> If anyone can send me an explanation or drawing, it would me much
> appreciated.
>
> Steve
>
> On Mon, Oct 25, 2021 at 19:19, Schechner, Sara 
> wrote:
>
>> Hi Steve,
>> The photo of the azimuth dial is hard to read.  I don't know what screws
>> you are talking about preventing the arm from turning.  The arm is
>> backwards at the moment since the pointed end should be on the scale of
>> hour lines.  I am not convinced that there is a flap on the square end of
>> the arm for a vane.  The sun at most angles would not fall far along the
>> arm to reach the other end where the slot is.  Rather, I suspect there was
>> a vertical gnomon in the slot at the pointed end.  Its shadow could have
>> been aligned with the point so that the point was in line with the sun's
>> azimuth.  As for the round dial, it almost always shows minutes and is
>> geared to the rotation of the arm.
>>
>> That's my best guess.
>> Sara
>>
>> -Original Message-
>> From: sundial  On Behalf Of Steve Lelievre
>> Sent: Monday, October 25, 2021 1:22 PM
>> To: Sundial List 
>> Subject: What's the inner scale on this photo for?
>>
>> Hi,
>>
>> Today a website called Vermont Free Press published an appallingly
>> confusing (to me) summary of types of sundials. If you can bear to look,
>> it's at https://www.vermontpressbureau.com/types-of-sundials/
>>
>> However, there was one thing about it that piqued my interest: the photo
>> of an azimuth sundial (
>> https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg
>> ).
>>
>>  From what I can make out, there is a metal flap at the end of the
>> alidade / sighting arm (the end at top in the photo). It must get turned up
>> to make a shadow-caster.  I guess the arm has to be rotated so that the
>> shadow falls along it, and time is then read from where the right-hand edge
>> of the arm crosses the net of hour and declination lines. But then,
>> wouldn't the screws seen in the upper plate block the arm from being turned
>> to the required orientation?
>>
>> Another bit I can't figure is the little circular scale just north of the
>> centre of the dial, with the pointer. Perhaps just an Equation of Time
>> scale? Or perhaps a cam connects it to the arm so that it can be used to
>> set the arm's length? (The slot in the arm suggests it can be slid in and
>> out to set the tip at the applicable declination circle, which is a nifty
>> feature.)
>>
>> Cheers,
>>
>> Steve
>>
>> ---
>> https://lists.uni-koeln.de/mailman/listinfo/sundial
>>
>> --
> Cell +1 778 837 5771
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



Re: What's the inner scale on this photo for?

2021-10-29 Thread Steve Lelievre
Thank you, Sara and Patrick for your replies to my question.

I shall try to get to the Science Museum sometime to have a look at the
dial, if that can be arranged.

I’ve been trying to figure out how the cam that Sara mentioned might work.

I’ve never studied the working of cams and this case isn’t obvious to me as
there are two inputs, azimuth and declination, that must drive the minutes
shown.

If anyone can send me an explanation or drawing, it would me much
appreciated.

Steve

On Mon, Oct 25, 2021 at 19:19, Schechner, Sara 
wrote:

> Hi Steve,
> The photo of the azimuth dial is hard to read.  I don't know what screws
> you are talking about preventing the arm from turning.  The arm is
> backwards at the moment since the pointed end should be on the scale of
> hour lines.  I am not convinced that there is a flap on the square end of
> the arm for a vane.  The sun at most angles would not fall far along the
> arm to reach the other end where the slot is.  Rather, I suspect there was
> a vertical gnomon in the slot at the pointed end.  Its shadow could have
> been aligned with the point so that the point was in line with the sun's
> azimuth.  As for the round dial, it almost always shows minutes and is
> geared to the rotation of the arm.
>
> That's my best guess.
> Sara
>
> -Original Message-
> From: sundial  On Behalf Of Steve Lelievre
> Sent: Monday, October 25, 2021 1:22 PM
> To: Sundial List 
> Subject: What's the inner scale on this photo for?
>
> Hi,
>
> Today a website called Vermont Free Press published an appallingly
> confusing (to me) summary of types of sundials. If you can bear to look,
> it's at https://www.vermontpressbureau.com/types-of-sundials/
>
> However, there was one thing about it that piqued my interest: the photo
> of an azimuth sundial (
> https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg
> ).
>
>  From what I can make out, there is a metal flap at the end of the alidade
> / sighting arm (the end at top in the photo). It must get turned up to make
> a shadow-caster.  I guess the arm has to be rotated so that the shadow
> falls along it, and time is then read from where the right-hand edge of the
> arm crosses the net of hour and declination lines. But then, wouldn't the
> screws seen in the upper plate block the arm from being turned to the
> required orientation?
>
> Another bit I can't figure is the little circular scale just north of the
> centre of the dial, with the pointer. Perhaps just an Equation of Time
> scale? Or perhaps a cam connects it to the arm so that it can be used to
> set the arm's length? (The slot in the arm suggests it can be slid in and
> out to set the tip at the applicable declination circle, which is a nifty
> feature.)
>
> Cheers,
>
> Steve
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
> --
Cell +1 778 837 5771
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



RE: What's the inner scale on this photo for?

2021-10-25 Thread Schechner, Sara
Hi Steve,
The photo of the azimuth dial is hard to read.  I don't know what screws you 
are talking about preventing the arm from turning.  The arm is backwards at the 
moment since the pointed end should be on the scale of hour lines.  I am not 
convinced that there is a flap on the square end of the arm for a vane.  The 
sun at most angles would not fall far along the arm to reach the other end 
where the slot is.  Rather, I suspect there was a vertical gnomon in the slot 
at the pointed end.  Its shadow could have been aligned with the point so that 
the point was in line with the sun's azimuth.  As for the round dial, it almost 
always shows minutes and is geared to the rotation of the arm.  

That's my best guess.
Sara

-Original Message-
From: sundial  On Behalf Of Steve Lelievre
Sent: Monday, October 25, 2021 1:22 PM
To: Sundial List 
Subject: What's the inner scale on this photo for?

Hi,

Today a website called Vermont Free Press published an appallingly confusing 
(to me) summary of types of sundials. If you can bear to look, it's at 
https://www.vermontpressbureau.com/types-of-sundials/

However, there was one thing about it that piqued my interest: the photo of an 
azimuth sundial ( 
https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg
).

 From what I can make out, there is a metal flap at the end of the alidade / 
sighting arm (the end at top in the photo). It must get turned up to make a 
shadow-caster.  I guess the arm has to be rotated so that the shadow falls 
along it, and time is then read from where the right-hand edge of the arm 
crosses the net of hour and declination lines. But then, wouldn't the screws 
seen in the upper plate block the arm from being turned to the required 
orientation?

Another bit I can't figure is the little circular scale just north of the 
centre of the dial, with the pointer. Perhaps just an Equation of Time scale? 
Or perhaps a cam connects it to the arm so that it can be used to set the arm's 
length? (The slot in the arm suggests it can be slid in and out to set the tip 
at the applicable declination circle, which is a nifty feature.)

Cheers,

Steve

---
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---
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Re: What's the inner scale on this photo for?

2021-10-25 Thread Patrick Vyvyan
I'm afraid I can't give you any answers , but the original is in the
Science Museum, London. They don't give any clues either, but I guess you
could contact them
https://collection.sciencemuseumgroup.org.uk/objects/co143/azimuth-sun-dial-simple-azimuth-sundial

Best wishes,
Patrick Vyvyan

On Mon, 25 Oct 2021 at 14:23, Steve Lelievre <
steve.lelievre.can...@gmail.com> wrote:

> Hi,
>
> Today a website called Vermont Free Press published an appallingly
> confusing (to me) summary of types of sundials. If you can bear to look,
> it's at https://www.vermontpressbureau.com/types-of-sundials/
>
> However, there was one thing about it that piqued my interest: the photo
> of an azimuth sundial (
> https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg
> ).
>
>  From what I can make out, there is a metal flap at the end of the
> alidade / sighting arm (the end at top in the photo). It must get turned
> up to make a shadow-caster.  I guess the arm has to be rotated so that
> the shadow falls along it, and time is then read from where the
> right-hand edge of the arm crosses the net of hour and declination
> lines. But then, wouldn't the screws seen in the upper plate block the
> arm from being turned to the required orientation?
>
> Another bit I can't figure is the little circular scale just north of
> the centre of the dial, with the pointer. Perhaps just an Equation of
> Time scale? Or perhaps a cam connects it to the arm so that it can be
> used to set the arm's length? (The slot in the arm suggests it can be
> slid in and out to set the tip at the applicable declination circle,
> which is a nifty feature.)
>
> Cheers,
>
> Steve
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial



What's the inner scale on this photo for?

2021-10-25 Thread Steve Lelievre

Hi,

Today a website called Vermont Free Press published an appallingly 
confusing (to me) summary of types of sundials. If you can bear to look, 
it's at https://www.vermontpressbureau.com/types-of-sundials/


However, there was one thing about it that piqued my interest: the photo 
of an azimuth sundial ( 
https://www.vermontpressbureau.com/wp-content/uploads/2021/10/Azimuthal.jpg 
).


From what I can make out, there is a metal flap at the end of the 
alidade / sighting arm (the end at top in the photo). It must get turned 
up to make a shadow-caster.  I guess the arm has to be rotated so that 
the shadow falls along it, and time is then read from where the 
right-hand edge of the arm crosses the net of hour and declination 
lines. But then, wouldn't the screws seen in the upper plate block the 
arm from being turned to the required orientation?


Another bit I can't figure is the little circular scale just north of 
the centre of the dial, with the pointer. Perhaps just an Equation of 
Time scale? Or perhaps a cam connects it to the arm so that it can be 
used to set the arm's length? (The slot in the arm suggests it can be 
slid in and out to set the tip at the applicable declination circle, 
which is a nifty feature.)


Cheers,

Steve

---
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