Prime focusing help

Hi!

I have adn ED80, with a flip mirror. When I attach my Canon Digital Rebel to the flip with the proper T ring and adapter, I can't focus the camera at all. I've tried attaching the camera to the rear portion of the flip mirror so as to bypass the mirror altogether, but still just get no focus whatsoever, just a cream colored nothing.
Obviously I'm doing something wrong, but what? Being a newbie can be sooo frustrating!
All thoughts, ideas and suggestions will be very much appreciated.


TIA!

Mike

The trick here is getting enough in-travel in you focuser.

Does your camera come to focus when you attach it directly to the end of the drawtube? (no projection eyepiece, no diagonal, no flip mirror system---just the end of the telescope focuser directly into the camera adapter/t-ring/camera mount.)

If it does not (and it may not since the camera requires extra in-focus) then you will actually have to shorten the tube to get anything with your camera/tube combination.

If it does, then put your flip mirror into the end of the focuser tube, and attach your camera directly to the back of it. (There should be no other diagonal.) If it still comes to focus, then you are fine. This is how it is supposed to be used.

If it does not, then you will have to have a flip mirror system that takes up less distance. You may be able to cheat a few mm by removing a washer or an adapter or something--if you can still get the flip mirror system stable. (Most flip mirrors have their own camera adapter and do not need a separate one.) If yo cannot do this, you are back to shortening the tube itself again.

Alex

Hi Mike, 8)

You need to find out where the image comes to focus and put the chip of the camera there.

The easiest way I know of is to point your telescope at the moon and with nothing attached to it and the focuser tube all the way in. Take a piece of white paper and place it in the light path coming from the rear of the scope. By experimenting with the distance of the paper to the back of your scope you will find it focuses on the paper at a certain distance from the rear of your scope. This is your back focus and you must work around this measurement. Anything between your camera chip and the back of the scope must add up to a measurement that puts the chip there. This "anything" can include, extension tubes, the t-ring, the space between the front of your camera and it's chip and how much you move your focuser draw tube out.

Regardless

Where the light comes to focus on a scope is where the chip/film needs to be.