eyepiece projection

Dumb question perhaps, but when you do eyepiece projection
photography, can you focus by viewing at the eyepiece then mount the
rest of the hardware to take the photograph? I just focus at the
camera, but it seems that once the telescope is focused, the distance
between the eyepiece and the film plane is just altering
magnification. My gut feeling is no, because when you view at the
eyepiece, you are also compensating for your eyesight.

miso wrote:

Dumb question perhaps, but when you do eyepiece projection
photography, can you focus by viewing at the eyepiece then mount the
rest of the hardware to take the photograph? I just focus at the
camera, but it seems that once the telescope is focused, the distance
between the eyepiece and the film plane is just altering
magnification. My gut feeling is no, because when you view at the
eyepiece, you are also compensating for your eyesight.

If you focus your scope to infinity, ALSO assuming you have 20/20
eyesight (for the focusing eye), then you'd get enough slack to be able
to focus your camera AT the EP, without changing focus.

In this case, moving the camera away from the EP, doesn't change the
magnification, cause rays exiting the EP are parallel. This is not true
as you say, if you focus your scope for a myopic/hypermetropic eye, or
for closer than infinity. Then, you'd lose focus if you move the camera
away from the EP, since the rays between EP and camera lens won't be
parallel.
--
I. N. Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

"miso" wrote in message
om...
Dumb question perhaps, but when you do eyepiece projection
photography, can you focus by viewing at the eyepiece then mount the
rest of the hardware to take the photograph? I just focus at the
camera, but it seems that once the telescope is focused, the distance
between the eyepiece and the film plane is just altering
magnification. My gut feeling is no, because when you view at the
eyepiece, you are also compensating for your eyesight.

Is that like astral projection man?

CarboHolic wrote:
"miso" wrote in message
om...

Dumb question perhaps, but when you do eyepiece projection
photography, can you focus by viewing at the eyepiece then mount the
rest of the hardware to take the photograph? I just focus at the
camera, but it seems that once the telescope is focused, the distance
between the eyepiece and the film plane is just altering
magnification. My gut feeling is no, because when you view at the
eyepiece, you are also compensating for your eyesight.


Is that like astral projection man?



Given my results, I fear you are right :-)

Is that like astral projection man?



Given my results, I fear you are right :-)

you must have some results indeed.

My eyesight is only as good as my contacts. ;-) Well, it was an
interesting mental exercise. I only mentioned it because the last time
I was doing EP projection, I didn't remember how many extension tubes
are needed, so I looked out the eyepiece first to insure I had the
right number of extenders before hooking up the camera. It was so easy
to focus by viewing from the EP rather than the viewfinder of the
camera.

Google dragged up a few old EP projection posts. Quite a few
suggestions to use plossl EPs, but I know from experience you want an
ortho.

Ioannis wrote in message news:1094247352.401196@athnrd02...
miso wrote:

Dumb question perhaps, but when you do eyepiece projection
photography, can you focus by viewing at the eyepiece then mount the
rest of the hardware to take the photograph? I just focus at the
camera, but it seems that once the telescope is focused, the distance
between the eyepiece and the film plane is just altering
magnification. My gut feeling is no, because when you view at the
eyepiece, you are also compensating for your eyesight.

If you focus your scope to infinity, ALSO assuming you have 20/20
eyesight (for the focusing eye), then you'd get enough slack to be able
to focus your camera AT the EP, without changing focus.

In this case, moving the camera away from the EP, doesn't change the
magnification, cause rays exiting the EP are parallel. This is not true
as you say, if you focus your scope for a myopic/hypermetropic eye, or
for closer than infinity. Then, you'd lose focus if you move the camera
away from the EP, since the rays between EP and camera lens won't be
parallel.