Re: Apparent Distance
- From: Chris L Peterson <clp@xxxxxxxxxxxxxxxxxx>
- Date: Fri, 29 Apr 2005 20:15:54 GMT
On Fri, 29 Apr 2005 12:36:18 +0300, "Ioannis" <morpheus@xxxxxxxxxxxx>
wrote:
>The above though constraints (3) badly. For example:
>
>
>For the Moon, a = 1/2 degree, and OB ~ 380,000 km.
>
>
>After doing the appropriate conversions and plugging in the numbers, (4)
>gives a maximum magnification of 180x. However, it is well known that one
>can use magnifications in excess of x180 for the Moon for example.
>
>
>Why the apparent discrepancy?
If you move the Moon 180X closer (the apparent distance when using
180X), what is its actual distance from you? There is no single number
you can use. At large distances, you assume that the distance to the
center of the extended object is the same as the distance to the edge of
the object. But when things get close, that approximation falls apart.
If the Moon were physically 180 times closer, the distance from the
observer to the surface center and the observer to the limb would be
significantly different. That geometrical distortion doesn't occur when
you simply apply optical magnification, though.
In other words, the concept of apparent distance as you use it is
geometrically different from actually moving the object of study to that
calculated position, and that difference becomes significant when the
angles become large.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.
- References:
- Apparent Distance
- From: Ioannis
- Apparent Distance
- Prev by Date: Re: Starry Night Pro question
- Next by Date: Re: The big bang theory [ The Red Shift ]
- Previous by thread: Re: Apparent Distance
- Next by thread: Re: Apparent Distance
- Index(es):
Relevant Pages
|
