Recent content by Subdot

Thank you! Interesting that the Wikipedia page subtracts/adds the hour angle from the time of true solar transit, rather than from (720 - longitude*4). I would naively think that the Wikipedia page's suggestion is in theory more accurate? I tried an example, and this produces significant...

It seems to me, the way to determine whether NOAA's approximation is better than alternatives I've suggested in the thread is to know: 1) Is it true that we want the input time for the second pass to the equation of time, declination, etc. to be as close to the actual time as we can get? I...

I now understand why my naive way of doing things here is incorrect and NOAA's way is correct, thanks to the discussion. Basically, my concerns about finding the Julian day for the user's local midnight are already taken care of by subtracting the longitude in the solar noon function var tnoon =...

Confirming after just playing around with codepen that after choosing 1/6/2025, 2460681.5 is the input for solar noon, sunrise, and sunset, which means the time is computed at midnight, not noon. By various calculators, including the JPL, converting the 2460681.5 to a calendar date is not the...

Good thought, but I don't see how this is what is going on. The user inputs 1/6/2025 (any timezone). The julian day is computed for 1/6/2025 with the function getJD() in the OP. 1524.5 is subtracted at the end of this conversion, so the julian day is for 1/6/2025 at UTC midnight (so I...

Thank you! That is indeed what is happening. So now the big question: Is this correct? They are calculating the equation of time at the estimated local midnight in UTC for both the first and second pass. This is deliberate: if they wanted to calculate the equation of time at the estimated solar...

Thanks for the response! Sorry for the huge delay. I had a lot to do and had some travel. I'm struggling to see how this might happen. Could you walk me through it a bit? Suppose on the first pass that 1/20/2025 11:35 am local time is what is computed for solar noon. This is converted to a...

Calculations below to arrive at the Naval Observatory formula, if anyone is interested, and so I don't forget either! It was also fun to work through. We start with $$r = a\frac{1 - e^2}{1 + e\cos v},$$ where v is the true anomaly, a = 1.000001018 AU, and e is the orbital eccentricity =...

I have three questions in relation to algorithms used in calculating sunrise, sunset, and solar noon. I'm looking at the NOAA javascript (view source on their solar calculator page and then find the main.js file) and comparing some of the intermediate calculations to other algorithms, such as...

Thank you. This is helpful advice as always.

I am a first-year PhD student who worked with a professor over the summer. I get along very well with her, and I would be happy to work with her if I was certain that my interests aligned with hers. She is a very popular advisor and has a lot of students wanting to work with her, so she gave me...

I am by no means qualified to give advice on how to look for grad schools (seeing how I'm basically in the same situation), but this website seemed to me to give pretty helpful advice: http://www.physics.unh.edu/undergraduate/advice-physics-majors-grad I also recently found this from the APS...

Thanks for the responses. I shame that more than 3-4 grad courses would probably be difficult to do, but I suppose that is expected. I guess I'll have to choose those classes wisely (assuming I'm allowed to take them in whatever school I end up in). Funny! Just knowing myself, I wouldn't be...

I'm an undergraduate who finished up my junior year this past Spring. I've been looking around at grad schools for physics. However, I find myself about as unwilling to study physics in grad school and leave pure math behind, as I am unwilling to do things the other way around. Math so far has...

Gravitomagnetism is cool. I'm at FAU (just finished junior undergrad year). From what I recall, one of my fellow students asked about the physics PhD program during one of our classes, and apparently, there aren't enough faculty to run one. The reason they are heavily into theoretical physics...