Ultratelephoto photography is easily achieved with your Meade ETX spotting scope or telescope by purchasing this SLR camera adapter. You'll need to take precautions to minimize vibrations, such as locking up the camera's mirror if possible as well as using a cable release or remote control to fire the shutter.
This adapter has two parts; a threading and an extension tube. The combination is screwed on to the ETX-90/105/125 Maksutov-Cassegrain telescopes' rear cell threading, making the ETX-90 a 1450mm f/16.0, the ETX-105 an 1830mm f/17.4, nad the ETX-125 a 2130mm f/18.0 prime lens.
With APS-C style digital SLRs, it is possible to use this adapter without the vignetting-eliminating extension tube. You still may experience some minor vignetting, but you'll get a shorter and faster lens combination (ETX-90=1250mm f/13.8, ETX-105=1640mm f/15.6, & ETX-125=1900mm f/15.0).
Note: Your camera will need to be in fully manual exposure mode, although some brands of camera may also work in aperture-priority autoexposure mode. Additionally, if there is a switch on the camera which chooses the focus mode, that switch must indicate manual focusing.