May I wish you a warm welcome to the CameraLabs forums.
Although you own a Canon I think you are most likely to get best advice in the Technical and scientific photography
forum so I've moved your question here.
I have no experience with your type of telescope so all I can suggest is that a Barlow lens might solve your problem but you would need to check the optical specifications to make sure. Case 3 on this TeleVue page
The only caution I would offer is that on my TeleVue refractor exactly the opposite situation applied. Once I had removed the eyepiece assembly and fitted my camera the focal plane was actually behind the sensor at maximum draw-tube extension so I had to invest in an extension tube.