Revision as of 17:39, 16 December 2024

The horizon dip measurement is the angle between the horizontal (the line perpendicular to the vertical at a specific point) and the apparent horizon.

On a globe, we would expect this angle to increase with increasing altitude, because the horizon would drop away with the curve.

On a flat earth, we would expect the horizon to always "rise to eye level".

Instructions

If you want to submit your own, email dip@mctoon.net Please include the following detail with your submission:

1. A clearly visible horizon (ideally, no clouds at, or near the horizon)

2. An instrumented graphic overlay showing true horizontal

3. Altitude at time of photo

4. Date

5. Time with time zone

6. Image Source/Credit. Please indicate if you want to be credited and how. We do not wish to dox anyone but we do want to appropriately give credit where it is due.

Gallery

Note:
Some photos are cropped due to the size limit for uploaded files.


Source/Credit	<source>
Date	<date>
Time
Timezone	<zone>
Longitude	5.4E
Latitude	51.4N
Camera	ZWO ASI 120MM
Lens	Skywatcher Guidescope Evoguide 50 ED + IR passthrough filter

@@ Line 1: / Line 1: @@
 The horizon dip measurement is the angle between the horizontal (the line perpendicular to the vertical at a specific point) and the apparent horizon.
-On a globe, you would expect this angle to increase with increasing altitude, because the horizon would drop away with the curve. In fact, we can calculate the expected dip of the horizon for any altitude using this formula:
+On a globe, we would expect this angle to increase with increasing altitude, because the horizon would drop away with the curve.
-<math>
+On a flat earth, we would expect the horizon to always "rise to eye level".
-\text{Dip} = \sqrt{\frac{2h}{R}}
-</math>
-Where:</br>
+= Instructions =
-h = the height or altitude of the observation </br>
-R = the radius of the earth (6,378 km)
-Here is a table of the expected dip of the unrefracted horizon for various altitudes:
+If you want to submit your own, email dip@mctoon.net Please include the following detail with your submission:
-{| class="wikitable"
+.  A clearly visible horizon (ideally, no clouds at, or near the horizon)
-| style="background:#d0e5f5;text-align:center" | Altitude
-| style="background:#d0e5f5;text-align:center" | Dip
-|- halign="center"
-| 10,000 ft || 1.772°
-|-
-| 20,000 ft || 2.505°
-|-
-| 30,000 ft || 3.068°
-|-
-| 40,000 ft || 3.542°
-|}
-On a flat earth, if the plane is infinite, you would expect no drop of the horizon with increasing altitude. You would just be able to better resolve distant points because of the greater angular resolution between them. If the plan is finite, there would be slight dip of the apparent horizon from the horizontal, but not nearly as much as on the globe. We can calculate this expected dip for any altitude as well.
+.  An instrumented graphic overlay showing true horizontal
-Measurements will be forthcoming.
+.  Altitude at time of photo
+.  Date
+.  Time with time zone
+.  Image Source/Credit.  Please indicate if you want to be credited and how.  We do not wish to dox anyone but we do want to appropriately give credit where it is due.
+= Gallery =
+'''Note:'''<br>Some photos are cropped due to the size limit for uploaded files.
+<div class="sunspots">
+{{Sunspot
+|image=File:Sunspot-20241207-0956-Dora.png
+|Source/Credit=<source>
+|date=<date>
+|time=<time>
+|tz=<zone>
+|long=5.4E
+|lat=51.4N
+|camera=ZWO ASI 120MM
+|lens=Skywatcher Guidescope Evoguide 50 ED + IR passthrough filter
+}}