I recently discovered that UCSD has something called the
High Performance Wireless Research & Education Network (HPWREN) that includes web cameras mounted on the masts around the local San Diego county high points. I started checking them regularly for visibility before decisions whether or not to go out for any observations. I didn't consider the resolution sufficient for what I've been trying to do in investigating flat vs. globe earth.
But I happened to catch the moon setting this morning on one of the camera feeds, which gave me the idea that maybe it might capture the sunset and let us gauge where the horizon is with respect to level. But rather than collect the imagery and try to assess it, I thought it might be my interesting to make some predictions beforehand and THEN see how it played out.
This is just a rough cut, but according to the HPWREN web site, and in looking at the views from other cameras, I deduce that the western facing camera is at an elevation of ~1600'. Mt Soledad in La Jolla is 822' at distance of 66,222' away, and so that gives me an index line: 0.7° declined below level sight (we'll go with a flat earth measure; on a globe with std refraction, eye level would be 0.1° higher).
On a globe, instead of the horizon being at eye level, it should be declined 0.65° from that 1600' vantage point. In a bit of serendipity, Mt. Soledad summit seems to coincide with the globe "horizon," below the FE eye level "horizon".
How to gauge the angular dimension? That nearby water tank is 32' from ground to edge of the domed top. Working out the trig (I forget the distance off hand), it's about 0.5°. So that provides a pixel/degree ratio basis, and using that is how I can place the eye-level line above the Mt. Soledad summit line (and projected globe earth horizon line).
Does that follow? The sun is about 0.5° in angular diameter too, but I don't expect we'll see its actual size without a filter. The haze low on the western horizon may filter the sun enough to see it as an orb.
Looking at TimeandDate, the sun should set at 6:35PM on the 267° azimuth. It looks to me like the camera is oriented on 270°, and that seemed to be corroborated by the earlier moonset bearing. So I placed an arrow where I think the sun will set.
I'd like to refine these lines and measures using the larger resolution photo instead of this reduced image (reduced for the purpose of posting it inline and not wrecking the page). But I wanted to get this posted now, just in case I don't get back to it before sunset.
Anyone can check and see if the prediction was close. Will the sun appear to set below the eye level line? Will the time and bearing of TimeandDate.com match what I'm predicting?
Here's the direct link to the web cam. Under 3 hours to sunset.
Edit:
I see the sun is already in view, and now see that the disc is being eclipsed. I don't know if that will remain in place all the way through to sunset.
And it's looking grim for my globe estimate. Sure looks like the horizon is appearing to be raised above the Soledad summit, just about the level I figured was FE eye level...though the image below is cropped from the original at double the resolution than my annotated one above. Nevertheless, my estimate of globe earth horizon is looking wrong. Depends on the haze.
Either my geometry/trig was way off or that sun eclipsing disk is well greater that 0.53°.
Update #2:
I don't. GoogleEarth depicts the globe horizon just barely cresting the summit of Mt Soledad when height is set at 1600' from the Black Mtn view point.
Update #3:
Still looking like horizon is around 0.5° above Mt. Soledad summit. (
Large JPG file, annotated)
Update #4:
Raw image at sunset. Will assess tomorrow, but anyone can do it.
Update #5:
Looking at this morning's camera feed and at last night's file capture of sunset, I find myself asking lots of questions. When I initiated this topic, I was nervous because my globe earth calculation of where the horizon should be compared with where it appeared to be was so different. But from lower elevations, I'm well-familiar with what the atmospheric haze and marine layer can do to make the actual horizon difficult to see. But seeing from the vantage point of 1600' I wasn't so sure. And as I watched the sun illuminate the ocean and appear to make the horizon distinguishable, I thought I was going to have to eat my hat and score one for flat earth.
It shouldn't have been a surprise to me, but it was when I checked the archived picture after sunset -- I missed the actual event live -- and saw the sun setting below the apparent horizon. I still have to mark it up and measure, but just eyeballing it, it sure looks close to the prediction.
The azimuth was way off from predicted though, but that's just my error since I was guessing that the camera was pointed due west. I checked the bearing line with GoogleEarth and the sun DID set on a bearing of 267°. So now I know how the camera is oriented.
The time was off as well, by a couple of minutes. But I forgot that from a higher elevation the time, of course, will slew later. Local hot air balloons give their customers multiple sunset viewings by climbing through higher altitudes. I should have known the time of sunset would be later.
But that horizon: even this morning, looking at the feed, I could swear the horizon is higher.
And looking at last night's shot, the sun is setting on a bearing line just about in line with the northern tip of San Clemente Island, but I can't detect any hint of the island in the image. MAYBE there's a tip of Mt Thirst poking up above the marine layer. Or, I might be just trying to see something that isn't there.