<p>(Figured it out)</p>
<p>The Horizons system is showing the times in UT, whereas NOAA is showing in local time.</p>
<p>Also, Elevation of 180 degrees is not sunrise. Additionally, that first column is Apparent Azimuth, which is appoximately 180; the second column is the Apparent Elevation</p>
<p>Apparent Elevation of 0 occurred at around 00:51 UTC, which is 6:21 AM.</p>
<p>The upper edge of the disc should be visible when sun's elevation is approximately -0.833 degrees, which is approximately 00:47:30 UTC (~6:17:30 AM), which matches with the NOAA output of 06:18 AM</p>
<pre><code> 2021-Nov-14 00:47 C   108.397078  -0.907623
 2021-Nov-14 00:48 C   108.454956  -0.677355
 2021-Nov-14 00:49 C   108.513138  -0.447165
 2021-Nov-14 00:50 C   108.571625  -0.240194
 2021-Nov-14 00:51 *r  108.630419  -0.049586
 2021-Nov-14 00:52 *   108.689521   0.141888
 2021-Nov-14 00:53 *   108.748934   0.335242
 2021-Nov-14 00:54 *   108.808659   0.530992
</code></pre>

CC BY-SA 4.0
2021-11-14T04:56:00.497Z
2021-11-14T07:13:36.357Z
2021-11-14T07:13:36.357Z
Pradyumna
<p>I used the NOAA solar calculator at <a href="https://gml.noaa.gov/grad/solcalc/" rel="nofollow noreferrer">https://gml.noaa.gov/grad/solcalc/</a> to generate the sunrise time for today.</p>
<pre><code>Location 12.95793 (latitude), 77.6257038 (longitude)
Timezone +530
Date: 14th November 2021 India Standard Time
</code></pre>
<p>It showed the sunrise at 06:18 AM. (Apparent Sunrise).</p>
<p>I also used the Horizons system at <a href="https://ssd.jpl.nasa.gov/horizons/app.html#/" rel="nofollow noreferrer">https://ssd.jpl.nasa.gov/horizons/app.html#/</a> with these settings:</p>
<pre><code>Type: Observer Table
Target Body: Sun [Sol]
Observer Location: Bangalore India (77°18′00.0″E, 13°48′00.0″N)
Time Specification: Start=2021-11-14 06:10 UT , Stop=2021-11-14 06:40, Step=1 (minutes)
Table settings: &quot;Apparent AZ and EL&quot;
Refraction model: Standard Atmospheric Refraction Model
</code></pre>
<p>It showed the apparent elevation to be 180 at around 06:36. So the sunrise should be around 06:36 as per Horizons.</p>
<pre><code> 2021-Nov-14 06:29 *   177.223563  57.880717
 2021-Nov-14 06:30 *   177.669462  57.891349
 2021-Nov-14 06:31 *   178.115626  57.900093
 2021-Nov-14 06:32 *   178.562003  57.906948
 2021-Nov-14 06:33 *   179.008542  57.911912
 2021-Nov-14 06:34 *   179.455191  57.914986
 2021-Nov-14 06:35 *   179.901898  57.916167
 2021-Nov-14 06:36 *t  180.348610  57.915457
 2021-Nov-14 06:37 *   180.795277  57.912855
 2021-Nov-14 06:38 *   181.241846  57.908361
 2021-Nov-14 06:39 *   181.688265  57.901977
</code></pre>
<p>Why is there a big (~18 minutes) difference between the two?</p>
<p>(It's cloudy here and I don't have an unobstructed view of the horizon, so I can't actually see when the sunrise happened).</p>

CC BY-SA 4.0
2022-05-17T03:49:33.583Z
BTW, the `t` indicator in the Horizons output stands for "transit". It's showing you the UTC time of apparent noon at that location, when the Sun transits the meridian.
PM 2Ring
<nasa><sunrise>
Difference in Sunrise times between Horizons and NOAA
Pradyumna
# Difference in Sunrise times between Horizons and NOAA

(Asked by: username_0 on 2021-11-14)

I used the NOAA solar calculator at https://gml.noaa.gov/grad/solcalc/ to generate the sunrise time for today.
Location 12.95793 (latitude), 77.6257038 (longitude)
Timezone +530
Date: 14th November 2021 India Standard Time

It showed the sunrise at 06:18 AM. (Apparent Sunrise).
I also used the Horizons system at https://ssd.jpl.nasa.gov/horizons/app.html#/ with these settings:
Type: Observer Table
Target Body: Sun [Sol]
Observer Location: Bangalore India (77°18′00.0″E, 13°48′00.0″N)
Time Specification: Start=2021-11-14 06:10 UT , Stop=2021-11-14 06:40, Step=1 (minutes)
Table settings: "Apparent AZ and EL"
Refraction model: Standard Atmospheric Refraction Model

It showed the apparent elevation to be 180 at around 06:36. So the sunrise should be around 06:36 as per Horizons.
 2021-Nov-14 06:29 *   177.223563  57.880717
 2021-Nov-14 06:30 *   177.669462  57.891349
 2021-Nov-14 06:31 *   178.115626  57.900093
 2021-Nov-14 06:32 *   178.562003  57.906948
 2021-Nov-14 06:33 *   179.008542  57.911912
 2021-Nov-14 06:34 *   179.455191  57.914986
 2021-Nov-14 06:35 *   179.901898  57.916167
 2021-Nov-14 06:36 *t  180.348610  57.915457
 2021-Nov-14 06:37 *   180.795277  57.912855
 2021-Nov-14 06:38 *   181.241846  57.908361
 2021-Nov-14 06:39 *   181.688265  57.901977

Why is there a big (~18 minutes) difference between the two?
(It's cloudy here and I don't have an unobstructed view of the horizon, so I can't actually see when the sunrise happened).

**Tags:** nasa, sunrise

> **Comments:**
> **username_1**: BTW, the `t` indicator in the Horizons output stands for "transit". It's showing you the UTC time of apparent noon at that location, when the Sun transits the meridian.  

---

## 1 answers

### Answer by username_0 on 2021-11-14. Score: 3

(Figured it out)
The Horizons system is showing the times in UT, whereas NOAA is showing in local time.
Also, Elevation of 180 degrees is not sunrise. Additionally, that first column is Apparent Azimuth, which is appoximately 180; the second column is the Apparent Elevation
Apparent Elevation of 0 occurred at around 00:51 UTC, which is 6:21 AM.
The upper edge of the disc should be visible when sun's elevation is approximately -0.833 degrees, which is approximately 00:47:30 UTC (~6:17:30 AM), which matches with the NOAA output of 06:18 AM
 2021-Nov-14 00:47 C   108.397078  -0.907623
 2021-Nov-14 00:48 C   108.454956  -0.677355
 2021-Nov-14 00:49 C   108.513138  -0.447165
 2021-Nov-14 00:50 C   108.571625  -0.240194
 2021-Nov-14 00:51 *r  108.630419  -0.049586
 2021-Nov-14 00:52 *   108.689521   0.141888
 2021-Nov-14 00:53 *   108.748934   0.335242
 2021-Nov-14 00:54 *   108.808659   0.530992


---

