How to improve the quality of an image of the planets when taken through the eyepiece of a telescope with a dlsr camera
If you were using both a camera lens and an eyepiece (afocal method), try eyepiece projection.
In this method, the eyepiece is the only optical element between the prime focus and the detector.
You would need an eyepiece projection adapter tube to connect the camera body to the telescope's focuser.
A longer tube will increase magnification but also increase exposure time.
Any tube length which reasonably balances those concerns should be OK.

It's also possible to use a Barlow lens and no eyepiece to extend the effective focal length of the telescope.
If your adapter tube is wide enough to accommodate the Barlow, you may be able to use it this way too.

Astronomy Source has an article with more details about eyepiece projection.
Tele Vue has an overview of that and other methods, plugging their own products of course.