An interesting Astronomical Question

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An interesting Astronomical Question

Postby rene-gedaly » Mon Feb 06, 2017 11:52 am

BACKGROUND
I received the intriguing email below and forwarded it to the HAS membership to take a crack at it. This post preserves the discussion and tools used to answer the question.
Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.

Hoping you can help with date ( and hope for a clear & sunny morning).


:D Rene

image002.png

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I received the question below; it was sent to our [email protected] email account.

​​Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.

Hoping you can help with date ( and hope for a clear & sunny morning).


The photo of the monstrance he refers to is at the end. I answered his question in part this way:


What an interesting question! One would think you'd see the illuminated monstrance at the same time and date in 2017 as 2016. However, last year was a leap year; we had a Feb 29. On Dec 31, 2016, we also added a ​l​eap ​s​econd (but that's too small a time unit to worry about).

So​,​ is the time you'd see this again in 2017 exactly on February 25 at 7:38 a.m.? Well, no. There are other perturbations in the way we keep time that factor into ​the​ exact time.​

So far I haven't answered your question. I'd like to forward it to the membership of the Houston Astronomical Society to see what they come up with. We have some accomplished amateurs who might like to take a crack at your question. But I should be able to email you an answer, or at least a time range, soon.​​



The perturbations I was thinking about have to do with sidereal year vs. regular (tropical) year, precession, lunation, etc. Okay, well some of these will have more effect than others.

Am I making this more complicated than it need be? Time is complex, after all.

I'd be interested to hear what you have to say. When should this person start looking for the illuminated monstrance this year? See below.

Rene




Steve Fung
Feb 4 (2 days ago)

to HAS
Rene,

Cool picture - reminds me of the Map Room scene in Indiana Jones and Raiders of the Lost Ark when Indy uses the Staff of Ra. I would think this is a projectional geometry problem with sun's position determined throughout the year as an analemma with window of solution(s) also depending on width of the sun ray through the window and size of the monstrance.

Steve

Sent from my iPhone

On Feb 4, 2017, at 7:10 PM, Rene Gedaly <[email protected]> wrote:

I received the question below; it was sent to our [email protected] email account.

​​Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.

Hoping you can help with date ( and hope for a clear & sunny morning).


The photo of the monstrance he refers to is at the end. I answered his question in part this way:


What an interesting question! One would think you'd see the illuminated monstrance at the same time and date in 2017 as 2016. However, last year was a leap year; we had a Feb 29. On Dec 31, 2016, we also added a ​l​eap ​s​econd (but that's too small a time unit to worry about).

So​,​ is the time you'd see this again in 2017 exactly on February 25 at 7:38 a.m.? Well, no. There are other perturbations in the way we keep time that factor into ​the​ exact time.​

So far I haven't answered your question. I'd like to forward it to the membership of the Houston Astronomical Society to see what they come up with. We have some accomplished amateurs who might like to take a crack at your question. But I should be able to email you an answer, or at least a time range, soon.​​



The perturbations I was thinking about have to do with sidereal year vs. regular (tropical) year, precession, lunation, etc. Okay, well some of these will have more effect than others.

Am I making this more complicated than it need be? Time is complex, after all.

I'd be interested to hear what you have to say. When should this person start looking for the illuminated monstrance this year? See below.

Rene

<monstrance.png>

HAS Forums: https://www.astronomyhouston.org/forum/

Facebook Group: https://www.facebook.com/groups/AstronomyHouston
Web and e-mail hosting for club members $10.00/Mo. for 250Gig storage. [email protected]
HAS Forums: https://www.astronomyhouston.org/forum/

Facebook Group: https://www.facebook.com/groups/AstronomyHouston
Web and e-mail hosting for club members $10.00/Mo. for 250Gig storage. [email protected]

Rene Gedaly <[email protected]>
Feb 4 (2 days ago)

to HAS
I don't think that's all of it. But it's the bulk of it.


Mark Ferraz
Feb 4 (2 days ago)

to HAS
He'd have to have it in the same spot and at the same angle I'd assume as well

-Mark Ferraz

On Feb 4, 2017, at 7:10 PM, Rene Gedaly <[email protected]> wrote:

I received the question below; it was sent to our [email protected] email account.

​​Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.

Hoping you can help with date ( and hope for a clear & sunny morning).


The photo of the monstrance he refers to is at the end. I answered his question in part this way:


What an interesting question! One would think you'd see the illuminated monstrance at the same time and date in 2017 as 2016. However, last year was a leap year; we had a Feb 29. On Dec 31, 2016, we also added a ​l​eap ​s​econd (but that's too small a time unit to worry about).

So​,​ is the time you'd see this again in 2017 exactly on February 25 at 7:38 a.m.? Well, no. There are other perturbations in the way we keep time that factor into ​the​ exact time.​

So far I haven't answered your question. I'd like to forward it to the membership of the Houston Astronomical Society to see what they come up with. We have some accomplished amateurs who might like to take a crack at your question. But I should be able to email you an answer, or at least a time range, soon.​​



The perturbations I was thinking about have to do with sidereal year vs. regular (tropical) year, precession, lunation, etc. Okay, well some of these will have more effect than others.

Am I making this more complicated than it need be? Time is complex, after all.

I'd be interested to hear what you have to say. When should this person start looking for the illuminated monstrance this year? See below.

Rene

<monstrance.png>



Steve Fung
AttachmentsFeb 4 (2 days ago)

to HAS
Rene,

Here's a fun website http://www.sunearthtools.com/dp/tools/p ... php#annual that you can go to. I entered 10135 West Rd, Houston, TX 77064 (Lat 29.9084913, Lon -95.5687655) and set the time to 2016/02/26, 07:38 GMT-6. It then computes the solar azimuth and altitude for not just the given time (Az 105.61 deg, Alt 8.94 deg) but also for the entire year, displayed as polar and Cartesian graphs and can be downloaded as a table. See enclosed PDF. Excel file too large to enclose. It turns out that the sun is in similar position on 2016/10/15 around 07:05-07:10. I did not compute it for 2017, but it follows pretty much the same steps I mentioned above.

Attachments area

Don Sailing
Feb 4 (2 days ago)

to HAS
I have a program that will display the suns alt-azimuth coordinates. I believe that is what is important for what you are trying to do. Keep in mind, it computes the coordinates based on the average atmospheric conditions. Different atmospheric conditions may cause some inaccuracies.

For the date of 02/26/2016 at 7:38 AM I got the following alt-azimuth coordinates:
Altitude = 9.04°
Azimuth = 106°

I tried to get the times for the sun to be at the same coordinates this year. However since the program only lists it to the minute, I was not able to get the exact coordinates. There are two days in which I got the same azimuth (rounded to the nearest degree). I listed the minute before and after the altitude of 9.04° so you could extrapolate if you need to.

Sun Rise Thu Feb 23 06:54:04 CST 2017
02/23/2017 Thu 07:40 AM
Altitude = 8.94°
Azimuth = 107°

Sun Rise Fri Feb 24 06:53:03 CST 2017
02/24/2017 Fri 07:39 AM
Altitude = 8.96°
Azimuth = 106°
02/24/2017 Fri 07:40 AM
Altitude = 9.17°
Azimuth = 106°

Sun Rise Sat Feb 25 06:52:02 CST 2017
02/25/2017 Sat 07:38 AM
Altitude = 8.99°
Azimuth = 106°
02/25/2017 Sat 07:39 AM
Altitude = 9.19°
Azimuth = 106°

Sun Rise Sun Feb 26 06:50:59 CST 2017
02/26/2017 Sun
Altitude = 9.01°
Azimuth = 105°

I also listed two dates later this year that will have the same coordinates.

Sun Rise Mon Oct 16 07:24:56 CDT 2017
10/16/2017 Mon 08:11 AM
Altitude = 8.99°
Azimuth = 106°

Sun Rise Tue Oct 17 07:25:36 CDT 2017
10/17/2017 Tue 08:12 AM
Altitude = 9.04°
Azimuth = 106°

Don Sailing


From: [email protected] [mailto:[email protected]] On Behalf Of Rene Gedaly
Sent: Saturday, February 04, 2017 7:11 PM
To: [email protected]
Subject: [HAS] An interesting astronomical question!
HAS Forums: https://www.astronomyhouston.org/forum/



Steve Fung
Feb 4 (2 days ago)

to HAS
I agree with Don's computations. Using SunEarthTools.com, I also came up with a window of Feb 24-26 around 7:35 am to get the same solar altitude and azimuth position.


Steve

On Sat, Feb 4, 2017 at 10:06 PM, Don Sailing <[email protected]> wrote:
I have a program that will display the suns alt-azimuth coordinates. I believe that is what is important for what you are trying to do. Keep in mind, it computes the coordinates based on the average atmospheric conditions. Different atmospheric conditions may cause some inaccuracies.

For the date of 02/26/2016 at 7:38 AM I got the following alt-azimuth coordinates:
Altitude = 9.04°
Azimuth = 106°

I tried to get the times for the sun to be at the same coordinates this year. However since the program only lists it to the minute, I was not able to get the exact coordinates. There are two days in which I got the same azimuth (rounded to the nearest degree). I listed the minute before and after the altitude of 9.04° so you could extrapolate if you need to.

Sun Rise Thu Feb 23 06:54:04 CST 2017
02/23/2017 Thu 07:40 AM
Altitude = 8.94°
Azimuth = 107°

Sun Rise Fri Feb 24 06:53:03 CST 2017
02/24/2017 Fri 07:39 AM
Altitude = 8.96°
Azimuth = 106°
02/24/2017 Fri 07:40 AM
Altitude = 9.17°
Azimuth = 106°

Sun Rise Sat Feb 25 06:52:02 CST 2017
02/25/2017 Sat 07:38 AM
Altitude = 8.99°
Azimuth = 106°
02/25/2017 Sat 07:39 AM
Altitude = 9.19°
Azimuth = 106°

Sun Rise Sun Feb 26 06:50:59 CST 2017
02/26/2017 Sun
Altitude = 9.01°
Azimuth = 105°

I also listed two dates later this year that will have the same coordinates.

Sun Rise Mon Oct 16 07:24:56 CDT 2017
10/16/2017 Mon 08:11 AM
Altitude = 8.99°
Azimuth = 106°

Sun Rise Tue Oct 17 07:25:36 CDT 2017
10/17/2017 Tue 08:12 AM
Altitude = 9.04°
Azimuth = 106°

Don Sailing


From: [email protected] [mailto:[email protected]] On Behalf Of Rene Gedaly
Sent: Saturday, February 04, 2017 7:11 PM
To: [email protected]
Subject: [HAS] An interesting astronomical question!

I received the question below; it was sent to our [email protected] email account.

​​
Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.

Hoping you can help with date ( and hope for a clear & sunny morning).


The photo of the monstrance he refers to is at the end. I answered his question in part this way:


What an interesting question! One would think you'd see the illuminated monstrance at the same time and date in 2017 as 2016. However, last year was a leap year; we had a Feb 29. On Dec 31, 2016, we also added a
​l​
eap
​s​
econd (but that's too small a time unit to worry about).

So
​,​
is the time you'd see this again in 2017 exactly on February 25 at 7:38 a.m.? Well, no. There are other perturbations in the way we keep time that factor into
​the​
exact time.​

So far I haven't answered your question. I'd like to forward it to the membership of the Houston Astronomical Society to see what they come up with. We have some accomplished amateurs who might like to take a crack at your question. But I should be able to email you an answer, or at least a time range, soon.
​​




The perturbations I was thinking about have to do with sidereal year vs. regular (tropical) year, precession, lunation, etc. Okay, well some of these will have more effect than others.

Am I making this more complicated than it need be? Time is complex, after all.

I'd be interested to hear what you have to say. When should this person start looking for the illuminated monstrance this year? See below.

Rene



HAS Forums: https://www.astronomyhouston.org/forum/

Facebook Group: https://www.facebook.com/groups/AstronomyHouston
Web and e-mail hosting for club members $10.00/Mo. for 250Gig storage. [email protected]
HAS Forums: https://www.astronomyhouston.org/forum/

Facebook Group: https://www.facebook.com/groups/AstronomyHouston
Web and e-mail hosting for club members $10.00/Mo. for 250Gig storage. [email protected]

HAS Forums: https://www.astronomyhouston.org/forum/

Facebook Group: https://www.facebook.com/groups/AstronomyHouston
Web and e-mail hosting for club members $10.00/Mo. for 250Gig storage. [email protected]

Steve Fast
Feb 4 (2 days ago)

to HAS
The position of the person and the angle of the monstrance would also need to be the same. Or really the angle of incidence of the sun's ray and the angle of reflectance to the person would need to be equal.

Steve Fast

My work:
Fast Decision Solutions, LLC
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+1-713-898-2188

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Don Sailing
Feb 4 (2 days ago)

to HAS
I have to say that sunearthtools.com was a little more accurate than my calculations. For 02/26/2016 at 8:38 AM it got an altitude of 8.94° and I got an altitude of 9.04°. I went to JPL’s horizons and it got an altitude of 8.97°. So that made sunearthtools.com off by -0.03° and my calculations off by +0.07°.
Sorry.
Don Sailing

From: [email protected] [mailto:[email protected]] On Behalf Of Steve Fung
Sent: Saturday, February 04, 2017 9:55 PM
To: [email protected]
Subject: Re: [HAS] An interesting astronomical question!


Rene Gedaly <[email protected]>
Feb 5 (1 day ago)

to HAS
So interesting! I hadn't known about sunearthtools.com--thanks, Steve Fung!--and admit my first blush idea was to start from first principles like Don, Mark, and Steve Fast did. I believe we've got a good enough range to give him an answer. I love the natural curiosity and utilitarian aspect of the question. Thanks, Guys.


Don Selle
Feb 5 (1 day ago)

to HAS
The perfect tool for this is an app called The Photographers Ephemeris. If you enjoy doing landscape photography this is the ultimate tool for planning your shoot.

http://photoephemeris.com/

Alan Dyer recommended it as one of the essential tools for nightscape photography in his 2015 talk at TSP. Its free to run in a browser on your desktop, the android version is $4.99 - have't tried the iOS version. It is map based and very intuitive to use. It has google maps functionality and sliders for time, so zeroing in on an answer is pretty quick.

Once you have the location, date and time, it will calculate the azimuth and altitude of the sun at that location. You can then choose any date and see if those figures can be duplicated, set the date and move the time slider until you get similar alt az numbers.

For this problem, TPE shows for the location St Maxamillian Kolbe Catholic Churrch on Feb 26 2016 at 07:38 the sun at alt: 9.0deg az:105.6 deg.

If I move to 2017 and scan dates and times close to one year later I get these results - some of which are very close:

02/24/17 : 07:35 alt:8.1 az:105.6 at 07:39 alt:9.0 az:106.1

02/25/17 : 07:36 alt:8.8 az:105.4 at 07:37 alt:9.0 az:105.7

02/26/17 : 07:37 alt:9.0 az:105.3 at 07:40 alt:9.6 az:105.7

I would guess that if the person who took the photo stood in the same position - weather permitting - a very similar photo could be taken.

Cheers

Don Selle
Cheers

Don Selle
[email protected]



Cheers

Don Selle
[email protected]


Rene Gedaly <[email protected]>
Feb 5 (1 day ago)

to HAS
Cool!


Steve Fung
Feb 5 (1 day ago)

to HAS
Agree - this is a great application for photography! I'm also glad that everyone's been correct about February 24-26, 7:35-7:40 am window.

Just to add a bit more, I thought this was a very interesting question that had a relatively simple answer, but it turns out quite a few nuances for computing solar position. Amazing what the internet can bring to one's fingertips these days.

The Wikipedia entry on computing position of the sun (https://en.wikipedia.org/wiki/Position_of_the_Sun) is from The Astronomical Almanac, published by the United States Naval Observatory (USNO) and based on J Meese. Astronomical Algorithms (1998) and by JJ Michalsky. The Astronomical Almanac’s algorithm for approximate solar position (1950–2050). J. Solar Energy 40 (1988).

More recently, this has been refined by I Reda and A Andreas. Solar position algorithm for solar radiation applications. Solar Energy 76 (2004) and revised publication by the National Renewable Energy Laboratory (NREL) in 2008.

I recommend the following NREL websites that has the technical report and C source code for the solar position algorithm (http://www.nrel.gov/midc/spa/) and other solar models and tools that may be of interest (http://www.nrel.gov/rredc/models_tools.html).


Rene Gedaly <[email protected]>
10:34 AM (23 hours ago)

to Steve, Steve
​I thought this was a very interesting question that had a relatively simple answer

​I know, right?! After a little thought, I started plugging and chugging the astro equations that use factors for precession and nutation. I'm sure glad I didn't post those! So much better to leverage the knowledge of the ages...the modern ages!


Steve Fung <[email protected]>
11:06 AM (23 hours ago)

to me
Yes, the internet is just amazing. I'm browsing the NREL website, and found the Solar and Moon Position Algorithm (SAMPA) that calculates the solar and lunar position in the period from year 2000 BC to 6000 AD with uncertainties of +/- 0.0003 degrees for the sun and +/-0.003 degrees for the moon.

http://www.nrel.gov/midc/sampa/

Given our upcoming August 21 total solar eclipse, I thought this may interest HAS members who want to know how to compute solar eclipses. This algorithm is by I Reda, who also wrote the NREL Solar Position Algorithm (SPA).


[email protected]
12:31 PM (21 hours ago)

to HAS
A very similar situation appears to occur at the airport Marriott Hotel in the rotating restaurant at the top. I worked in maintenance many, many years ago and discovered that on a certain few days twice a year, some buildings in downtown Houston reflected morning sunlight directly into the restaurant. On one foggy morning, the area near those buildings downtown appeared to be on fire. A very bright fire. I do not remember the exact dates but was near the Equinoxes. Somewhere I have a photograph of that foggy morning. It was well over 40 years ago and at that time was called the Host Hotel and the negative and pix is filed away somewhere.

Kenneth (drako) Drake

---- Steve Fung <[email protected]> wrote:
> Rene,
>
> Cool picture - reminds me of the Map Room scene in Indiana Jones and Raiders of the Lost Ark when Indy uses the Staff of Ra. I would think this is a projectional geometry problem with sun's position determined throughout the year as an analemma with window of solution(s) also depending on width of the sun ray through the window and size of the monstrance.
>
> Steve
>
> Sent from my iPhone
>
> > On Feb 4, 2017, at 7:10 PM, Rene Gedaly <[email protected]> wrote:
> >
> > I received the question below; it was sent to our [email protected] email account.
> >
> >> Last year I took a picture of this monstrance on February 26 at 7:38am. The sun was shining in & the rays hit just right to create this beautiful picture. I was wondering if you could tell me what day(s) the suns rays will be at the same position in the sky? I would love to watch this happen again. The chapel is located in Houston & address 10135 West Rd, 77064.
> >>
> >> Hoping you can help with date ( and hope for a clear & sunny morning).
> >
> >
> > The photo of the monstrance he refers to is at the end. I answered his question in part this way:
> >
> >>
> >> What an interesting question! One would think you'd see the illuminated monstrance at the same time and date in 2017 as 2016. However, last year was a leap year; we had a Feb 29. On Dec 31, 2016, we also added a leap second (but that's too small a time unit to worry about).
> >>
> >> So, is the time you'd see this again in 2017 exactly on February 25 at 7:38 a.m.? Well, no. There are other perturbations in the way we keep time that factor into the exact time.


Rene Gedaly <[email protected]>
10:21 AM (7 minutes ago)

to Steve
I think I'm going to have to copy this thread and post it to the Forums, Steve. Too much good info to lose.
You do not have the required permissions to view the files attached to this post.
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