Default magnification for a t-adapter

[zainraza]

As the title says, does the t adapter effect the magnification or would it be the camera you use?

I know you can get eyepiece projection adapters but just wondering what the default was like

[Capricorn]

The default is goverened by the scope focal length and is best not considered as magnification.

To magnify you need the scope and an eyepiece. The assumption is that you are using the image from the scope directly on the camera sensor - prime focus. So it is just a size.

The moon (1/2 deg) through a scope of 1000mm focal length would produce an image of about 8.7mm on the chip. No magnification just a size determined by the subtended angle and the focal length.

[Kevdan]

Sorry to Hi-jack the post but...

Does that mean that in theory a scope could use any size barlow for example a 750mmfl using a 5x barlow would work as this is only lengthening the focal length of the tube and not being used for maginification.

But how do you work out the sise of the image?

Kev.

[Ags]

width of sensor (in mm) * 57.3 / focal length (in mm)

=width of field shown by sensor

==============

You can use any image scale you like, but when the pixels on the sensor are smaller than the angular resolution of scope (as projected onto the chip) then further magnification is meaningless. Also, you are increasing the focal ratio, which makes the image dimmer.

[michael.h.f.wilkinson]

In photography, magnification is sometimes expressed as the focal length of the optical system divided by the focal length of the standard lens normally used for the sensor or film format. For the old 35mm format a 750 mm system has 750/50=15 times magnification. With a 5x barrow you would get 15x5=75 times magnification.

Another way to choose your optical configuration is to consider matching to the sensor resolution. For many webcams and CCDs the optimal focal ratio in terms of resolution is f/20. This has to do with the matching of the size of the diffraction disk to the size of the pixels. Note that this is relevant to compact, bright objects such as planets. For DSOs you generally want a fast system.

[brantuk]

The T-ring has no glass in it to magnify anything (mine doesn't at least) It's just a connecting ring with two different threads, if that's what you're asking

[Macavity]

As the title says, does the t adapter effect the magnification or would it be the camera you use?

I know you can get eyepiece projection adapters but just wondering what the default was like

If you are indeed using eyepiece projection, then it is possible to use e.g. JUST a bare adaptor with screw thread on the end of Baader Hyperions. But "magnification" varies quite rapidly with distance of the CCD plane from the "rear node" (wherever!) of the eyepiece. All a bit difficult to predict - And EASIER to measure experimentally.

http://www.alpineastro.com/Hyperion-Eyepieces_com/Images_and_Docs/Hyperion_Manual_2.pdf

In a specific circumstance, I found, a 24mm Hyperion gave "order of the same" image scale as prime focus.

[zainraza]

Oh right I think I get it now, so it really depends on focal length and yeah Brant that helps explain it a bit more now

That pdf is actually fairly helpful to be honest, I think I might just start off by using an orion steadypix deluxe camera mount as I just want to take simple pictures at the moment