adding a camera

[old39]

I am a little confused regarding putting any type of camera to your telescope. If you take out the eyepiece and replace it with a camera then haven't you lost your magnification,  or am I missing something.

Please help.

[Bizibilder]

If you remove the eyepiece and replace it with a camera sensor (no lens on the camera) then you are simply forming an image onto that sensor - ie the telescope objective (lens or mirror) acts in the same way as an "ordinary" camera lens - this is sometimes called "prime focus" imaging.  You can leave the eyepiece in place and still use a camera (with its own lens in place) to create an image - called eyepiece projection - but this tends to be restricted to simple "snapshots" of brighter objects like the Moon.

With my own DSLR (without lens) and a scope of around 900mm focal length I get a whole disc solar image like the one below:

[Knight of Clear Skies]

I find optics quite confusing as well, this diagram of a newtonian reflector may help.

Magnification is determined by the focal length of the scope then adjusted by the eyepiece. Adding an eyepiece manipulates the light cone, for example a high powered eyepiece takes light from the centre of the cone and enlarges it, at the cost of reduced brightness. Use of different eyepieces makes the telescope flexible but at high powers it is throwing away most of the light the scope collects.

[The Admiral]

... then haven't you lost your magnification,

Not really. You need to remember that the objective lens forms an image of the distant object; the eyepiece is used to view that image. It is true that the apparent size of the image you see, and hence the overall effective magnification, depends on the focal length of the eyepiece. But if you look at the simplified diagram below, where I've used a simple ray-tracing approach for two different focal length objective lenses, (a) and (b ), you can see that the image size will depend on how far the focused image is from the lens. For a longer focal length lens, it is larger.

If you place your camera where the image is focused, you can see that the image size produced by the camera will also depend on the focal length of the objective lens.

Hope that helps.

Ian

[ronin]

You have lost magnification as specific magnification. What you get is an image of a determined size on the camera sensor.

Equally if you have a camera and a lens you do not get magnification you simply get an image size on the camera sensor from the camera lens.

As the image size is dependant on the lens focal length then like a camera lens (zoom) the longer the focal length the bigger the image.