5 ms·
> This is 20% larger than the true value, 3960 mi Whoa, that is not insignificant error. What contributes to an error of this size?
by wyldfire 5y ago
> This is 20% larger than the true value, 3960 mi
Whoa, that is not insignificant error. What contributes to an error of this size?
- Keyframe 5y agoI don't think refraction would impact the error as much as a focal length of the camera. Probably both however.
- Tabular-Iceberg 5y agoWhat’s the effect of the focal length?
- KineticLensman 5y ago> What’s the effect of the focal length? Not sure what the GP intended, but one possible effect is that increasing the focal length ('zooming in') would change the relative size of two objects (one closer, one further away) depending on their relative distance to the camera (I think the closer object might appear relatively larger). But if the sun and the horizon are the intended objects, they are both effectively at infinity, from the camera's perspective, so I wouldn't expect focal length to change anything in this case.
- terramex 5y agoChanging focal length of a lens ('zooming in') does not change relative size of two objects, it is a common misconception. What changes relative size of objects are your legs when you move from one spot to another to get roughly the same framing with different focal lengths. If you stand in one spot and zoom or change prime lenses relative object sizes stay the same.
- KineticLensman 5y agoFair point - I should have tried this with an actual camera. But I suspect my line of reasoning still stands, that the focal length doesn't affect the phenomena being discussed here
- Keyframe 5y agohttps://fstoppers.com/architecture/how-lens-compression-and-perspective-distortion-work-251737 https://fstoppers.com/architecture/how-lens-compression-and-...
- dahart 5y agoThat article specifically clarifies that moving the camera is what causes changes to relative sizes, not the focal length. But in the experiment described, the camera doesn’t move a significant difference with respect to the sun, the camera can’t really get anywhere close enough to the sun or the reflection on the horizon to make any difference, certainly not 20%.
- thatcherc 5y agoMy bet would be refraction of the sunlight through the atmosphere. At sunrise and sunset light that reaches you on the ground is taking just about the longest path through the atmosphere that it can, and gradient of the atmosphere's density is definitely going to add some bending to the light coming in from space.
- sixbrx 5y agoYeah, it's significant enough that my astro mount has a "King tracking rate" to account for this effect. Named for Edward King. https://en.wikipedia.org/wiki/Edward_Skinner_King https://en.wikipedia.org/wiki/Edward_Skinner_King
- 123pie123 5y agoI was going to say something similar "we can see the Sun even when it is geometrically just below the horizon, at both sunrise and sunset. This is because of the refraction of the light from the Sun by the Earth's atmosphere--the Earth's atmosphere bends the path of the light so that we see the Sun in a position slightly different from where it really is." see http://curious.astro.cornell.edu/our-solar-system/52-our-solar-system/the-sun/observing-the-sun/194-why-can-we-see-the-sun-s-image-before-sunrise-and-after-sunset-beginner http://curious.astro.cornell.edu/our-solar-system/52-our-sol...
- rrss 5y agoVanderbei’s linked articles have some discussion of sources of error. The main one seems to be waves making the reflection appear longer.
- ffhhj 5y agoThe moon.
- jvanderbot 5y agoI expect the curvature of the earth has much less effect than refraction and mirage effects in causing this phenomenon.