1. Rory

    Rory Senior Member

    I don't really know for sure if there are trees on that part of Matinicus, though I suspect there are. No real idea how tall they'd be though. Wouldn't want to guesstimate. ;)

    And not really sure quite how the "stretched by refraction" specifically affects these calcs.

    Is it weird that there have been so many posts about a low quality image that doesn't really claim or show anything, and is easily explained? They're more addictive than sudoku, these pics! :D
     
  2. deirdre

    deirdre Moderator Staff Member

    you can see the trees on Google Earth and pull up property real estate pics to get a general idea :) I couldn't find the house at 72 feet elevation listed but some neighboring houses are available. ground is pretty hilly though so guesstimates are all we will get. They aint 0 feet though. :)
     
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  3. Rory

    Rory Senior Member

    I must've missed where that was posted; that's the house at the end of Ice Pond Lane, at 43.866210, -68.887392, with nice tall trees all around it? ;)

    Here's my final figures for this pic then, which will hopefully be useful to @eenor for when he does his tests next year:

    Elevation of lawn above mean sea level: 16 feet
    Elevation of camera above lawn: ~5.5 feet
    Distance to Marblehead Island: 2.56 miles (b)
    Elevation of summit of Marblehead: 33 feet amsl
    Distance to high point of NE portion of Matinicus (as seen to left of Marblehead):: 16.61 miles (y)
    High point of NE portion of Matinicus: ~105 feet amsl (including estimated 35 feet tree height)
    Level of water: 5.3 feet below mean sea level
    Camera height above water: 26.8 feet
    Summit of Marblehead above water: 38.3 feet (a)
    Summit of NE Matinicus above water: ~110 feet

    Predicted hidden amount of Marblehead (given standard refraction): None
    Predicted amount of Matinicus hidden: 54.5 feet
    Predicted amount of Matinicus visible (including tree height): ~55 feet (x)

    Size in picture of Marblehead: 35 pixels
    Size in picture of Matinicus: 9 pixels
    Relative size in picture: 3.9x
    Predicted relative size in reality: 4.5x (using (a/b)/(x/y))
    Predicted amount of Matinicus visible using relative sizes: 63.9 feet (using 9ay/35b)

    So it actually appears that there isn't that much extra refraction happening, as far as the highest point of the island is concerned: indeed, if the trees at that highest point are 43 feet tall, the image matches perfectly with what is predicted for standard refraction. And if they're 35 feet tall, it only requires refraction to be about +10% of standard for that to fit - well within 'normal range'.
     
    Last edited: Sep 7, 2017
  4. Trailblazer

    Trailblazer Moderator Staff Member

    This photo (and others by the same person on Flickr) gives you an idea. There are some pretty tall trees on the island.
    IMG_5172.PNG

    https://flic.kr/p/9abZLR
     
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  5. eenor

    eenor Member

    Thanks for all the thoughts, i put the trees at 50 feet tops, but will have to do more research to confirm, i know fisherman in the area that can perhaps give more detail. I'll plan to set up a better test next summer, better camera, exact tide levels, time lapse photos over a longer time span, and possibly a video of boat ride from Crescent Beach directly to Matinicus. My burn is that if Matinicus island visibility is truly refracted from behind horizon, moving towards it on a boat (for the umpteenth time in my years) will i be able to discern the point when the island is actually in view and no longer in view as refracted (which i still think is a thin explanation given superior mirage atmospheric requirements and the fact Ive seen it for decades as shown in many conditions)? If i can see a transition, then great, refraction it is... I'll see a change of some sort...But if i can't, than it still could be fairytale science terminology to explain away uncomfortable anomaly about our measurable reality. I'm open to that, despite general globe model bias all around, but I'd rather confirm the curve math... Less ostracism. It's only recently, learning about many laser tests of curve that i even questioned the view, i always thought i was looking directly at Matinicus, and frankly, i still do. But i can appreciate that more precise documentation detail is required now and i think I've at least established that a better experiment is worth doing.
     
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  6. Rory

    Rory Senior Member

    It seems like you are expecting a sharp 'transition point' between where the line of sight is more curved and less curved; would you say that's right?

    But would you not, rather, expect any transition to be smooth and gradual?

    It almost seems that, by taking these photos, you want to disprove that refraction exists. Would you say that's an accurate assessment of why you're doing this?
    If the trees are 50 feet tall, that makes the high point of NE Matinicus about 125 feet above the water. With standard refraction hidden amount of 55 feet, that would mean 70 feet of Matinicus would be visible. That seems pretty reasonable. And that, in your words, you are "looking directly at Matinicus".

    Also just to say: I appreciate your communication style and endeavour to be accurate in all this, as well as your openness to listen to the thoughts of others: a rare thing among people who have doubts about the shape of the earth. Cheers! :)
     
    Last edited: Sep 7, 2017
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  7. Trailblazer

    Trailblazer Moderator Staff Member

    You still seem to be mixing up mirages with regular refraction. Superior mirages are a fairly rare occurrence. Refraction is always present to some extent. It's a gradual effect, stronger closer to the surface, so you probably wouldn't notice any "transition" as you approach the island.
     
  8. eenor

    eenor Member

    -9 low tide at crescent beach is from a local old timer, our tide there goes out pretty far from high water mark, way more than in Rockland (which is nearby), we used to have to occasionally dive at high tide to find our mooring to tie off skiff, was over our head, so I'm confident it's at least 7 feet lower at Low tide, -9 doesn't sound wrong to me, and the old timers are serious about knowing depths for where the ledges are.

    The 300+ house disappearance comment was based on curve calculator and my iPhone locator distance given of 23 miles from Crescent Beach when i mapped from my standing location on lawn to Matinicus, still trying to figure out why that differs from Google online (yes all drawing of lines shows roughly 16 miles) and trying to get more info on that as Google misplaces Matinicus locator out to sea north of the actual island, best guess is that it's a generality because M island is actually an archepelago of a few islands. Any other ideas why they would differ? Are cell towers usually that off with GPS... Or FPS? ;)
     
  9. eenor

    eenor Member

    Thanks, back acha. I have no agenda beyond understanding. Until i get a better camera to see if i can see lower rocks of M island shore, I'm not sure now I'm looking at whole island from lawn position, though it appears to be whole based on sailing memory of its outline, can't confirm that yet, but from binoculars on rock position, based on curve, i think M island should be out of view. That's my main curiosity, that and understanding the details of what is required for refraction to create a mimic view, which are uncommon, yet my view of M island is very common.
     
  10. Rory

    Rory Senior Member

    Not sure. Sometimes there are just mistakes. I know if you find one online you can just right-click and 'report a problem'.
    Have you been reading much about refraction?

    One thing I would suggest: go on Google Earth and get a close up image of the entire lefthand part of the island. Then scale that down and superimpose it over the island in your photo. This should reveal a few things: whether or not the whole island is visible; how much of the land to the NW you're seeing (ie, is the land below 20 feet obscured by the horizon, or is it there?); and also whether there's any stretching and other distortion, etc.

    I can understand, being as you live there, being curious about the refractive effects in your locality. But for how refraction works as a whole, I'd probably look elsewhere for my understanding (books, papers, etc).

    It is interesting that you say it's "always" like this: I'm a bit skeptical as to whether that could be true, but I'm sure we'll find out next year. :)
     
    Last edited: Sep 7, 2017
  11. deirdre

    deirdre Moderator Staff Member

    refraction isn't uncommon. that's why there is a thing called "standard refraction".

    You think your view of M- which you can only see through binoculars- is common, but truth is we don't always recollect things we aren't paying attention to. For ex, I described the weather last month as 'weird', but the truth is maybe it always goes from freezing to sweltering to freezing to hot in August and I just don't really remember the dates because I never had much reason to pay that much attention to it. If you vacation there the same time every year you probably remember better than I would.

    Since you have access to an area with a identifiable landmark, more experiments.. over several days, would be cool as I am curious at how much refraction can change too. Perhaps some of your fisherman friends can keep a better eye out too over the year.

    If you boat out to Matinicus, try to get photos of the island when you know it is not behind the curve, too. the shape of the whole island in profile will also help you determine how much of the island we are actually seeing.
    and if you can note whether there is a high pressure area overhead (like on the 28th) or low pressure (the local weather news will tell you on tv) that would be cool too.. to me anyway, as I'm curious about refraction too as I don't have easy access to a place for experiments myself. (or a good enough camera)
     
  12. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    One could get a nasty scratch planting rulers. Tele_0_20170907163917. On the other hand nobody is going to move it, and the resolution is about 5 microradians.
     
    Last edited: Sep 7, 2017
  13. eenor

    eenor Member

    Binoculars were for the camera, i could see island with head close to low tide rock, less of it for sure, but very visible unassisted.
     
  14. deirdre

    deirdre Moderator Staff Member

    i have no idea what you are saying. :)
     
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  15. deirdre

    deirdre Moderator Staff Member

    do you spend a lot of your vacation time over the years with your head close to a high low tide rock studying the horizon? :)

    which is neither here nor there as I was talking about you sitting on the lawn looking at the ocean.
     
  16. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Really?
     
  17. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    I need to place a scale ~1 mile away (as shown) to measure the variation of refraction accurately. I'm not sure it is worth the effort.. Tele_0_20170907163917 cropped.
     
  18. deirdre

    deirdre Moderator Staff Member

    I see now. that is from your home? the pic doesn't really look like it has any refraction, so I wasn't sure if you were just making a general pricker joke.
     
  19. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    No shimmer, but as you know, there is always atmospheric refraction, even when is raining and blowing half a gale :)
     
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  20. deirdre

    deirdre Moderator Staff Member

    you're right. My sloppy wording doesn't help with a topic that is confusing enough already!
     
  21. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Yes, it is not going to move up and down much since I printed some fancy tripod footwork. feet.
     
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  22. eenor

    eenor Member

    Chuckling, you make a good point
     
  23. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Tide is up now, but house has not moved. Tele_0_20170908093604.
     
  24. Ph_

    Ph_ Closed Account

    Could you make these 2 fotos with that slider effect to compare them?
     
  25. Trailblazer

    Trailblazer Moderator Staff Member

    I've boosted the contrast a bit on the low-tide one.

    pic1. pic2.
     
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  26. Ph_

    Ph_ Closed Account

    Nice one, thanks.
    I think i see some difference in the refraction, points where the bushes are exactly aligned in the forground have some discrepancy in alignment with the buildings in the background, especially on the right side.

    edit:added:

    I think this is mainly due to a difference in temperature gradient, as the water should be colder in the morning in relation to the earth.
    The humidity should be greater in the afternoon as well when the water has warmed up a bit, both affect the refraction if i remember correctly.
     
    Last edited: Sep 8, 2017
  27. Trailspotter

    Trailspotter Senior Member

    It looks like the clouds have not moved too. Is this photo actually an overlay of the low- and high-tide photos?
     
  28. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    No clouds. What you can see in the distance is all land and buildings near Llanrhystud from Aberystwyth (Wales, UK), The side of the near hill is Pen Dinas. The window was closed for the second photo so a bit more blurred and possibly some distortion, but otherwise the same. Vertical field of view ~0.3 degrees for both, but I am fiddling with different reducers etc. at the moment, Telescope with webcam.

    It is not the horizon one can see, but the shore with some waves breaking up the beach, but it is not far from the horizon. Buildings should be fine for seeing refraction _changes_.
     
    Last edited: Sep 8, 2017
  29. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Too windy and overcast at the moment. I will try again if we see the sun again this year..
     
  30. Trailblazer

    Trailblazer Moderator Staff Member

    See the comparison slider image I posted above.
     
  31. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    More fun than watching paint dry. Tele_0_20170908135507.
     
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  32. Trailspotter

    Trailspotter Senior Member

    Actually, it was your comparison that prompted my question, because I mistook white buildings for clouds :oops:
     
  33. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    I have come to the conclusion that the horizon does not move much due to refraction at 50 metres above ground at my location. Things might be different over a desert close to the ground, but 50 metres above ground looking over the sea, with a prevailing onshore wind not a lot happens. Tele_0_20170923102826.
     
  34. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    The good news is that if I can see sheep at 22km. I should be able to see any flying at 36,000 ft.
     
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  35. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    The horizon is a bit beyond Newquay today, usually it is a bit closer, Tele_0_20170923102726.
     
  36. Rory

    Rory Senior Member

    Is this an interesting idea, similar to Canigou?

    The beach at Carlsbad in California is just the right distance away from Santa Catalina Island to hide the tallest peak: 64 miles, which should just about exclude Mount Orizaba (at 2,097 feet).

    Another nice feature of Carlsbad is that, around May 18th-May 22nd the sun will be setting right behind Santa Catalina Island (and also August 20th-24th).

    Looks like it would be pretty easy to do something like have two cameras filming the sunset from different elevations - one which should show nothing of the island (given standard refraction) and one which should show it silhouetted against the sun.

    Thought experiment for now.
     
  37. Mick West

    Mick West Administrator Staff Member

    You would have to be quite lucky with the weather. Catalina is often invisible from Santa Monica, which is quite a bit closer.
     
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  38. Rory

    Rory Senior Member

    How about sending JTolan there with his infrared filter? He lives just up the road. :)
     
  39. Vogon

    Vogon New Member

    Further to the Allauch-Canigou view. Quite a few photos appear to have the island of Pom├Ęgues, just under or just to the right of the Canigou sighting.

    This cannot happen from the church at Allauch. It's to the left of the mountain by a significant amount. So Jeran is using his deception-by-omission tricks again.