Quote:
Originally Posted by silv
one last question:
if it turns out that I can not get focus with the lens off (just a feeling),
how do I then subtract the 18mm lens from the measured length of the focal path to get the focal point of the assumed lens-off situation?
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The simple method is find the difference of focus. Use any eyepiece and focus on object 100/200 meter and mark on the focus tube. Now use the same eyepiece and focus on star and mark on the focus tube. Now you have difference of let say 20mm. Now mount your camera on telescope bring same object 100/200 meter away to focus. You have to take focuser all the way down to achieve focus. If get the focus and you still have few mm to travel in, minus this few mm from the focusing difference that you get from the eyepiece, whatever difference you get that much you have to move your primary.
Even if you can't get focus, then move the primary with existing collimating screw, this is how I did to find the difference. I had the same GSO ota that was mentioned in the review.