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