Zmanim information

[Joseph....@gmail.com]

I assume the zmanim information in iPhobe Siddur depends on sunrise
and sunset estimates, which are derived from the 'gps' location on the
iphone. How precise are these estimates? I was surprised to find that
when I check various sources (on the web) for sunset times for a
location there was some variability (could be a minute or two
difference).

[KosherJava]

The algorithm's for calculating zmanim are pretty standardized, and
most use the US Naval Observatory algorithm. The main reason that you
might see discrepancy is that
1) How do you know that the calendar that you are comparing to uses
the exact location? One end of a city to the other can be pretty far
apart. Some calendars do not enter the exact location, but rather
round off the longitude/latitude to the nearest minute, or just use
the general zip code location

2) some show seconds, some round the number (up or down), while other
calendars just truncate the seconds.

3) some use elevation, some do not. This can lead to a sizable
difference.

4) errors/variations on part of different calendar implementations.
These are very easy to creep into code, even when trying to follow an
exact algorithm. For an example of this, see
http://www.kosherjava.com/2008/04/13/fix-to-noaa-sunrisesunset-algorithm/

The bottom line is, that you have to compare apples and Apples
(capitalization intentional :) ), something very hard to do in this
case.
You can go to http://www.kosherjava.com/zmanim-project/zmanim-calendar-generator/
and zoom into your exact location, generate a calendar and compare,
the 2 algorithms (USNO and NOAA), and try it with, and without
elevation. You will need the ability to open an Excel file to read
this data. To see the exact elevation, longitude and latitude used for
zmanim on the iPhone, click on "About These Times" at the bottom of
the zmanim list in the iPhone. It would be nice if the Siddur gave an
option to show seconds, since you would be able to better compare
them.
Keep in mind that atmospheric temperature, barometric pressure and
humidity all affect sunrise/set. This is the reason that most
calendars have disclaimers, and the time should never be relied on
exactly. The only value in seconds would be to be able to properly
compare one calendar to another.

KosherJava

On Sep 28, 10:58 am, "Joseph.Mezr...@gmail.com"

[Victor Grazi]

In a related question - in the Syrian community (and I always though
all sephardim im the usa) the Magen Avraham calculations produce
different results than yours. We base ours on the day starting at
sunrise minus 1/10th of hours between sunrise and sunset. And ending
at sunset + 40 clock minutes. Then the rest of the calcs are standard
- shema is 1/4 of that day, amida is 1/3, hatzot is 1/2, minha ketana
is hatzot + 1/2 clock hour etc

Would it be possible to provide that as an option

[KosherJava]

Victor,
I assume that you use Alos, zman Krias Shema, and zman Tfila based on
this calculation. The siddur uses the KosherJava Zmanim API, and the
zmanim that you are looking for can be seen at
http://www.kosherjava.com/zmanim/docs/api/net/sourceforge/zmanim/ComplexZmanimCalendar.html#getAlos72Zmanis()
. In the same class, see getSofZmanShmaMGA72MinutesZmanis() etc. The
documentation needs some work, but this should be what you are looking
for (I will fix the Javadocs in the next day or so to be clearer).
Please confirm the zmanim by generating a spreadsheet at
http://www.kosherjava.com/zmanim-project/zmanim-calendar-generator/ .
At some point, I hope that the developers of teh Siddur will expand on
the number of zmanim available, and allow you to select the zmanim
that you would like displayed by default.
Thanks

On Sep 28, 12:42 pm, Victor Grazi <vgr...@gmail.com> wrote:
> In a related question - in the Syrian community (and I always though  
> all sephardim im the usa) the Magen Avraham calculations produce  
> different results than yours. We base ours on the day starting at  
> sunrise minus 1/10th of hours between sunrise and sunset. And ending  
> at sunset + 40 clock minutes. Then the rest of the calcs are standard  
> - shema is 1/4 of that day, amida is 1/3, hatzot is 1/2, minha ketana  
> is hatzot + 1/2 clock hour etc
>
> Would it be possible to provide that as an option
>

> On Sep 28, 2008, at 11:35 AM, KosherJava <kosherj...@gmail.com> wrote:
>
>
>
> > The algorithm's for calculating zmanim are pretty standardized, and
> > most use the US Naval Observatory algorithm. The main reason that you
> > might see discrepancy is that
> > 1) How do you know that the calendar that you are comparing to uses
> > the exact location? One end of a city to the other can be pretty far
> > apart. Some calendars do not enter the exact location, but rather
> > round off the longitude/latitude to the nearest minute, or just use
> > the general zip code location
>
> > 2) some show seconds, some round the number (up or down), while other
> > calendars just truncate the seconds.
>
> > 3) some use elevation, some do not. This can lead to a sizable
> > difference.
>
> > 4) errors/variations on part of different calendar implementations.
> > These are very easy to creep into code, even when trying to follow an
> > exact algorithm. For an example of this, see

> >http://www.kosherjava.com/2008/04/13/fix-to-noaa-sunrisesunset-algori...

>
> > The bottom line is, that you have to compare apples and Apples
> > (capitalization intentional :) ), something very hard to do in this
> > case.

> > You can go tohttp://www.kosherjava.com/zmanim-project/zmanim-calendar-generator/

[KosherJava]

Victor,
I see that I misread you. You state that

"We base ours on the day starting at sunrise minus 1/10th of hours
between sunrise and sunset. And ending at sunset + 40 clock minutes."

Can you provide a source for this "Asymmetrical" day? The sources that
I use (and there are a few that use an asymmetrical (greater offset
for Alos than tzais)) never mentioned the one that you mentioned. It
is easy enough to implement in my API, but a source would be welcome.

On Sep 28, 12:42 pm, Victor Grazi <vgr...@gmail.com> wrote:

> In a related question - in the Syrian community (and I always though  
> all sephardim im the usa) the Magen Avraham calculations produce  
> different results than yours. We base ours on the day starting at  
> sunrise minus 1/10th of hours between sunrise and sunset. And ending  
> at sunset + 40 clock minutes. Then the rest of the calcs are standard  
> - shema is 1/4 of that day, amida is 1/3, hatzot is 1/2, minha ketana  
> is hatzot + 1/2 clock hour etc
>
> Would it be possible to provide that as an option
>

> On Sep 28, 2008, at 11:35 AM, KosherJava <kosherj...@gmail.com> wrote:
>
>
>
> > The algorithm's for calculating zmanim are pretty standardized, and
> > most use the US Naval Observatory algorithm. The main reason that you
> > might see discrepancy is that
> > 1) How do you know that the calendar that you are comparing to uses
> > the exact location? One end of a city to the other can be pretty far
> > apart. Some calendars do not enter the exact location, but rather
> > round off the longitude/latitude to the nearest minute, or just use
> > the general zip code location
>
> > 2) some show seconds, some round the number (up or down), while other
> > calendars just truncate the seconds.
>
> > 3) some use elevation, some do not. This can lead to a sizable
> > difference.
>
> > 4) errors/variations on part of different calendar implementations.
> > These are very easy to creep into code, even when trying to follow an
> > exact algorithm. For an example of this, see

> >http://www.kosherjava.com/2008/04/13/fix-to-noaa-sunrisesunset-algori...

>
> > The bottom line is, that you have to compare apples and Apples
> > (capitalization intentional :) ), something very hard to do in this
> > case.

> > You can go tohttp://www.kosherjava.com/zmanim-project/zmanim-calendar-generator/

[KosherJava]

Victor,
A few phone calls and I found out that these are the zmanim by Rabbi
Raful of Brooklyn. What is interesting about the calculation is that
it leads to issues for Chatzos (it would not be at sundial/solar noon
(sun's transit of the zenith)), and Rabbi Reful does not want to relay
on this for Tzais, only for zman krias shema, Tfila and possibly the
end of fasts (besides yom kippur). If I do add this to the API, it
will have to be with a large disclaimer and warning, and it would
probably be prudent to only add it for zman krias shema, and tfila. In
addition, the time is for the NY area year round, with no correction
for the seasons, and it is not clear how exactly to calculate this for
other areas. My calculation show that the sun is about 8.41 degrees
below the horizon at this point during the equinox. I am not sure if
this solar dip can be used to apply these calculations for other
locals.

I hope that the Barry doesn't mind this slightly off Siddur topic.

[Victor Grazi]

I generate the spreadsheet for today for Lakewood.
It looks like the Alot I mentioned is in the spreadsheet as "Alos 72 Minutes Zmaniyos"
I don't see a value for Tzais matching the calculation I described

I wish I had a source for this, but I don't. It was introduced to me years ago when I lived in Deal NJ by Rabbi Shmuel Choueka.
It is the calculation used universally at Yeshivat Ateret Torah (Rabbi Yosef Harari-Raful)
It is the calculation used among the whole Syrian community; Iwill try to find a printed source.

Much thanks, Victor Grazi

[Joseph....@gmail.com]

Thanks for this detailed response, much appreciated. I presume the
zmanim alogroithm you describe is the one used in the iPhone siddur
program.

On Sep 28, 10:58 am, "Joseph.Mezr...@gmail.com"
<Joseph.Mezr...@gmail.com> wrote:

[Barry Schwartz]

Interesting conversation here. KosherZmanim, let me know what you
decide. We will try to add all the features you feel are important,
since you are really the expert in this category.

On Sep 28, 10:51 pm, "Joseph.Mezr...@gmail.com"

[KosherJava]

Barry,
I am still working on adding these zmanim to my API (the technology
part is easy, once I can clarify the proper way to calculate these
zmanim out of the NY area). In the meantime, since such zmanim are not
something that would interest everyone, can you start working on an
interface that would allow users to select the zmanim that they would
like to see by default? This will allow users to easily add/remove
zmanim.
Thanks

[Barry Schwartz]

Ill try to convince Ronnie to work on this part sooner than later...