Is this FOV calculator okay for telescope lenses?

Among 14 related free programs, you can try «T-Calc», «TelOpticulator»
and «Telescope Optical Parameters Calculator». Perhaps one of them
will suite your needs.

Take a look at:

http://astrotips.com

Downloads Windows Telescopes, ATM & optics

Regards,
HDV

"Richard" wrote in message ...
http://www.bdimitrov.de/kmp/technology/fov.html

Mentions rectilinear lens.

Or is there a better FOV calculator for telescope type lenses on the
net? (I'm thinking telescope lenses maybe are not rectilinear).

"Richard" wrote in message
...
http://www.bdimitrov.de/kmp/technology/fov.html

Mentions rectilinear lens.

Or is there a better FOV calculator for telescope type lenses on the
net? (I'm thinking telescope lenses maybe are not rectilinear).


Maybe something like this is what you're looking for:

http://www.multimediamadness.net/wod...k_a_camera.htm

Jeroen.

"Richard" wrote in message
...
http://www.bdimitrov.de/kmp/technology/fov.html

Mentions rectilinear lens.

Or is there a better FOV calculator for telescope type lenses on the
net? (I'm thinking telescope lenses maybe are not rectilinear).


Maybe something like this is what you're looking for:

http://www.multimediamadness.net/wod...k_a_camera.htm

Jeroen.

Richard wrote:
Richard wrote:


Okay, next, need to figure out focal distance.

Okay, let me see:

I think this is the formula:

1/di = 1/f - 1/do

Where di is the distance from the lens to the focal plane, do is the
distance from the object to the lens, and f is the focal distance of
the lens.

So:

1/di = 1/1200mm - 1/infinity

1/di = 1/1200mm

di = 1200mm.

Okay, let me think. We are saying that for a telescope of 1200mm focal
length the telescope body has to be appx 2400mm in length, in order to
place a focus plane in the rightspot?


Nope. I think I errored here and this is what I now think:

The focal distance of a lens is the distance to those places behind the
lens where parallel beams of light will converge. Thus, if there are
two distant objects, one on the left and one on the right in the field
of view, each would produce converging light at the focal distance, but
spacially seperated in the focal plane. Thus the distance to the focal
plane behind the lens equals the focal distance of the lens when the
object is at infinity.

When the object is not at infinity, covergeging rays for point sources
occur further back from the focal plane.

Thus the distance from the lens to the focal plane, (di), for a lens
with focal length of 1200mm is 1200mm.

As was said, "Where di is the distance from the lens to the focal
plane...".

I hope I am now correct.

Richard wrote:
Richard wrote:


Okay, next, need to figure out focal distance.

Okay, let me see:

I think this is the formula:

1/di = 1/f - 1/do

Where di is the distance from the lens to the focal plane, do is the
distance from the object to the lens, and f is the focal distance of
the lens.

So:

1/di = 1/1200mm - 1/infinity

1/di = 1/1200mm

di = 1200mm.

Okay, let me think. We are saying that for a telescope of 1200mm focal
length the telescope body has to be appx 2400mm in length, in order to
place a focus plane in the rightspot?


Nope. I think I errored here and this is what I now think:

The focal distance of a lens is the distance to those places behind the
lens where parallel beams of light will converge. Thus, if there are
two distant objects, one on the left and one on the right in the field
of view, each would produce converging light at the focal distance, but
spacially seperated in the focal plane. Thus the distance to the focal
plane behind the lens equals the focal distance of the lens when the
object is at infinity.

When the object is not at infinity, covergeging rays for point sources
occur further back from the focal plane.

Thus the distance from the lens to the focal plane, (di), for a lens
with focal length of 1200mm is 1200mm.

As was said, "Where di is the distance from the lens to the focal
plane...".

I hope I am now correct.