Another question (stupid) regarding photography via scopes

[Catanonia]

When I look through my ED80 scope with no eyepiece there is no magnification or that I can see straight through the tube.

Now when i put on the eyepiece it completes the optics and gives focal length / rating of eyepiece magnification.

So what happens when I put it directly onto my DSLR... Why do i get magnification ?

Does it just become a 600mm prime lens and if so what magnification does a dlsr on a 600mm prime lense give ? 600 / 35 = 17 times ???? (35 for 35mm dslr)

Now with eyepieces I can view upto 200x at saturn and see rings apparently. But at 600 prime on the dslr how the **** do I take a picture with the dslr to see this when I will be getting much lower magnifications ???

Do I have to attach the dslr to the eyepiece of the scope or something which would be very hard.

[troypiggo]

When you look through you bare scope with your naked eye there will be a point of focus, probably just that your head moves too much. The focuser on the telescope does the job of focusing the light onto some plane - when your camera is attached, the sensor plane.

Sorry, I don't know how to tell what magnification your images are.

I do have an ED80 and with a 4mm eyepiece you can make out Saturn and a line that you know is the rings, and also some of the brighter moons. You can't make out any surface detail though. For decent planetary viewing you really need something with a much bigger aperture and focal length. Recently I bought a C8 (2032mm f/10) Schmidt-Cassegrain and for the first time ever viewed Jupiter and moons. Could clearly make out the banding on the planet with 8mm eyepiece. Haven't viewed Saturn with it yet, too many clouds.

[Catanonia]

cheers mate, can anyone tell me what the mgnification is on a 600mm prime for a standard DSLR like a EOS 50D

[Catanonia]

worked it out.


50mm prime is considered normal eye ie 1:1

So a 500mm = 10 x magnification (roughly)

Now times by 1.6 as not a full frame

Means my 600mm Scope prime = (600 x 1.6) / 50 = 20 magnification.

[chris.bailey]

Dont think of it in terms of magnification as it is meaningless. Your scope brings to a point of focus an image. Depending on the size of you camera CCD, it records a prt of that image. Smaller CCD's "tend" to work better with lower priced scopes as the size and edge correction of that image will be smaller and not as well corrected as that from the triplets and quads.

Think of it in terms of Field of View. http://newastro.wodaski.com/ download CCD calc as that will give you your scope and CCD combinations field of view and image scale in relation to the object you are targeting.

[Bill Boehme]

So what happens when I put it directly onto my DSLR... Why do i get magnification ?

Does it just become a 600mm prime lens and if so what magnification does a dlsr on a 600mm prime lense give ? 600 / 35 = 17 times ???? (35 for 35mm dslr)

I don't think that the term magnification is relevant for this situation. We normally define the magnification power relative to looking at something with the unaided eye. For example, a scope with a certain eyepiece might produce an image of an extended object at 32 power meaning that the object will appear 32 times the size as viewed by the unaided eye. Conversely, with an image captured by a camera, it is a completely different situation since we don't know the size at which the image will be printed or viewed on a display screen.

The size of the sensor has nothing to do with how large the image will appear on it so we can't divide by 35 to get 17X..

To answer your question with an example, if you were using a direct objective set up (telescope with no eyepiece and no lens on the camera), the moon would project to a size of about 5.6 mm regardless of the size of the sensor or film. That would be a bit more than a third the height of an APS-C format sensor.

Now with eyepieces I can view upto 200x at saturn and see rings apparently. But at 600 prime on the dslr how the **** do I take a picture with the dslr to see this when I will be getting much lower magnifications ???

Do I have to attach the dslr to the eyepiece of the scope or something which would be very hard.

I think that the best set up for that situation might be a projection system -- telescope with eyepiece and no lens on camera.