Why can't I focus with my focal reducer in the light path?

[OzDave]

Hi,

I've got a 1500mm FL Maksutov scope and a Canon 450D camera that I use to image with. I also have a 0.5x Focal Reducer that was supplied with the scope.

When I use the focal reducer with an eyepiece, I can always get the image to focus. When I try to attach the focal reducer to the end of the camera T-adapter, however, all I can ever see thorugh the camera is an image of the mirror at the front of the scope, like what you see if you just look into the hole in the back of scope with nothing there.

I'm wondering why the focal reducer works with eyepieces, but not with the camera?

Do I need a different kind of focal reducer to go with the camera? If so, what sort of factor should I be looking for? Bonus points if you can explain why .

Thanks,

David

[GazOC]

Sounds like you've run out of in-focus. One solution may be to reduce the distance from the focal reducer to the DSLR chip. The greater that distance, the more in focus travel is required.

Is your focal reducer a 1.25" fitting that screws in? If so, they arn't really suitable for large chips like a DSLR and will show aberations away from the centre of the chip.

[Merlin66]

If the reducer is a 1.25" thread, then it's only suited to imaging with webcams. The focal length of the reducer will not allow it to find a focus > 20mm from it; the DSLR needs a minimum of 55mm....

You really need a "proper" reducer ie Celestron/ Meade SCT type BUT when I tried them there was severe vignetting due to the very small internal baffle on the Mak. Gave up in the end and just used the Mak for lunar/ planetary.

Ken