i nerd sniped myself tonight and i imagine the NSA operative who is assigned to me is very confused by the increasingly erratic and frustrated google searches for HOW DO I CALCULATE THE MOON WHERE IS THE MOON
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ok so back to the moon thing, i found another resource and i think i understand the why behind the asinine coordinate systems a little better but it also glosses over the math so it's kinda useless at the same time. i'm tempted to just make shit up and move on, but it would bother me that the function was wrong if i did that
@aeva is this one of those things where the approximate solution that drifts from reality by 0.0004% every year is like 3 lines and the more correct one is 5 pages of dense research and no one who writes about it is concerned with the idea that a reader may be a beginner and not know the difference
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ok so back to the moon thing, i found another resource and i think i understand the why behind the asinine coordinate systems a little better but it also glosses over the math so it's kinda useless at the same time. i'm tempted to just make shit up and move on, but it would bother me that the function was wrong if i did that
@aeva I love the way everyone uses different names for parameters, and does everything from the POV of an observational astronomer ... Really useful for simulation work.
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ok so back to the moon thing, i found another resource and i think i understand the why behind the asinine coordinate systems a little better but it also glosses over the math so it's kinda useless at the same time. i'm tempted to just make shit up and move on, but it would bother me that the function was wrong if i did that
@aeva i believe all our physical models diverge from reality on a long enough timescale. even quantum mechanics. every model is lossy compression / fitting of reality that we extrapolate from, starting at the time that the underlying measurements were taken.
best thing i can think of is measure exact position of celestial bodies, then run a sufficiently detailed n-body sim with best guesses for all state we can not measure, starting at that point. and then restart every year.
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@aeva is this one of those things where the approximate solution that drifts from reality by 0.0004% every year is like 3 lines and the more correct one is 5 pages of dense research and no one who writes about it is concerned with the idea that a reader may be a beginner and not know the difference
@halcy there's no closed form solution at all and from what i can tell the good solutions need to be rejiggered every few decades to stay accurate
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@halcy there's no closed form solution at all and from what i can tell the good solutions need to be rejiggered every few decades to stay accurate
@halcy the real problem here is that academic astronomy best practice is to tie everything into spherical coordinates on the firmament so they can factor out the earth enough that you can pretend it is a fixed vantage point that doesn't spin, and if god forbid you do need to tie an observation to geographic coordinates for some reason i guess you just burn an undergrad on it and not sully yourself with the indignity
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@halcy the real problem here is that academic astronomy best practice is to tie everything into spherical coordinates on the firmament so they can factor out the earth enough that you can pretend it is a fixed vantage point that doesn't spin, and if god forbid you do need to tie an observation to geographic coordinates for some reason i guess you just burn an undergrad on it and not sully yourself with the indignity
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@halcy the real problem here is that academic astronomy best practice is to tie everything into spherical coordinates on the firmament so they can factor out the earth enough that you can pretend it is a fixed vantage point that doesn't spin, and if god forbid you do need to tie an observation to geographic coordinates for some reason i guess you just burn an undergrad on it and not sully yourself with the indignity
@halcy i've got a feeling that this is what a self taught programmer feels when they try to work out how to sort stuff faster and everything they find is either programmers telling eachother to just use a library or academic formalist nonsense
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@halcy the real problem here is that academic astronomy best practice is to tie everything into spherical coordinates on the firmament so they can factor out the earth enough that you can pretend it is a fixed vantage point that doesn't spin, and if god forbid you do need to tie an observation to geographic coordinates for some reason i guess you just burn an undergrad on it and not sully yourself with the indignity
@aeva i guess that feels to me like it makes sense historically but maybe not…. anymore?
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today's extremely basic astronomy question that i'm finding surprisingly difficult to find an answer to: are geographic coordinates and equatorial coordinates the same coordinate system except one is for looking up and the other is for looking down, or is there some essential conversion step needed to correlate them?
@aeva geographic lat long is relative to the an ellipsoid. 0 degrees longitude is fixed to the surface of the earth.
Equatorial is a sphere and the longitude equivalent doesn’t rotate with the earth.
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@aeva geographic lat long is relative to the an ellipsoid. 0 degrees longitude is fixed to the surface of the earth.
Equatorial is a sphere and the longitude equivalent doesn’t rotate with the earth.
@jkaniarz where I currently am stuck is how do you convert between the three when it is not the vernal equinox
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@aeva i guess that feels to me like it makes sense historically but maybe not…. anymore?
@halcy well, historically astronomy was among other things at times significantly concerned with answering the question "where the hell am I", whereas modern astronomy seems to be more split between "what is that specific bright object" and "visible spectrum is cringe"
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ok so back to the moon thing, i found another resource and i think i understand the why behind the asinine coordinate systems a little better but it also glosses over the math so it's kinda useless at the same time. i'm tempted to just make shit up and move on, but it would bother me that the function was wrong if i did that
@aeva i have copies of the explanatory supplement to the astronomical almanac in case i ever get enough of an urge to write astronomical software – both the 1960s edition and the more recent third edition that takes into account modern atomic time and general relativity and 🤯
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@aeva i have copies of the explanatory supplement to the astronomical almanac in case i ever get enough of an urge to write astronomical software – both the 1960s edition and the more recent third edition that takes into account modern atomic time and general relativity and 🤯
@fanf I just put in an order for the 2025 Astronomical Almanac - what is this about an explanatory supplement?
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ok so back to the moon thing, i found another resource and i think i understand the why behind the asinine coordinate systems a little better but it also glosses over the math so it's kinda useless at the same time. i'm tempted to just make shit up and move on, but it would bother me that the function was wrong if i did that
after a good night's sleep and reflecting on what I've learned so far, I've decided to follow the classic computer science strat: when faced with a problem you don't know how to solve, simply do something else, and pretend that is what you meant to do all along.
not only are horizontal coordinates the choice reference frame for backyard astronomers, the "altitude h" angular measurement is probably closer to the solution I wanted than my earlier framing of the problem. narf
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@fanf I just put in an order for the 2025 Astronomical Almanac - what is this about an explanatory supplement?
@aeva https://aa.usno.navy.mil/publications/exp_supp roughly speaking it explains the mathematical models used to caclculate the almanac
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@jkaniarz where I currently am stuck is how do you convert between the three when it is not the vernal equinox
@aeva If you know the position at the previous equinox, I think it’s as simple as spinning the moon around the earth (in the plane of the moons orbit) for 2*PI*t/27.3 radians, then spinning the earth for 2*PI*t radians.
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@aeva https://aa.usno.navy.mil/publications/exp_supp roughly speaking it explains the mathematical models used to caclculate the almanac
@fanf that sounds useful. looks like it is out of print though?
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@mcc @cthos ah :( I was hoping Blacksky found a way around that problem, but I have no idea whether or not that is even possible because I have no idea how AT works.
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@cthos @aeva Every Bluesky replica is, probably without realizing it, making a bet that Bluesky has already plateaued.
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@cthos @aeva I don't have an answer to this question. I've seen various claimed attempts to ballpark this number, but I expect it will change month to month, so even if I trusted the numbers I saw (I don't) there's no guarantee they're still accurate.
The Big Problem as I see it is since every "tower" contains the entire network, if the amount of traffic on bluesky doubles, the operating costs of each tower doubles. The "oh shit this is harder than I thought" problem is even worse than fedi.
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@mcc @aeva Is there a good breakdown of the overall costs? Like I saw a lightweight AppView implementation still has to store roughly 2 gb of data per day, indefinitely, and...that's a _lot_ of storage.
I assume there's also a fair amount of bandwidth and other cost involved.
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@aeva The question as always with ATP though is "why?". That is *why* would anyone bother splitting from bluesky. What we've seen so far is two demographic communities with reasons to distrust platforms they don't operate themselves.
So like who else would bother? You wouldn't see like, a fishing community standing up their own tower because they have no reason to expect Bluesky will target them specifically, and it costs so much more than running a Mastodon instance.
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@aeva "Tower", that's a good word for it.
I think observably, the fact blacksky exists as a full stack (or at least end to end) example *is* inspiring more towers to stand up, and I'd put northsky as the example. (Or so I assume, I don't know for a fact the order of events.)
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@mcc do you think this work (on Blacksky or northsky's part) will lead to more independent atproto towers showing up in the future?
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Current* conditions near Fair Haven, MI:
