I have an older Mead EXT-?

I also just bought a Nikon D100 --- I have the T-ring and adapters, so am set to go. I'm having trouble finding the right aperture and shutter setting to give me a starting point for shots of the moon ---planets later. I'm 66 with bad eyesight and am tired of having to lug things back inside to see the settings buttons to try another shot --- flashlight doesn't make it Any body know where I should start, then I can work from there.

If you can read the indicators on the instruments you are using you have a problem. But I would expect a longish fraction of a second. Try one exposure at each click of the dial and then look at each result.

Without an idea as to the focal ratio of the optical system (the ETX90 or larger run about F13.8 to F15), I would only try bracket exposures of one stop or x2 or x1/2 the time either side of the suggested ones from Kodak:
Lunar Photography Exposure Guide (@f/16)
ISO Film Speed Full Moon Gibbous 1st Quarter Thick Crescent Thin Crescent
25---1/15--- 1/8--- 1/4--- 1/2--- 1
50---1/30--- 1/15--- 1/8--- 1/4--- 1/2
100---1/60--- 1/30--- 1/15--- 1/8--- 1/4
200---1/125--- 1/60--- 1/30--- 1/15--- 1/8
400---1/250--- 1/125--- 1/60--- 1/30--- 1/15
800---1/500--- 1/250--- 1/125--- 1/60--- 1/30.
1600---1/1000--- 1/500--- 1/250--- 1/125--- 1/60
3200---1/2000--- 1/1000--- 1/500--- 1/250--- 1/125
Exposure Times vs. ISO Film Speeds

"The speed (ISO) of the film being used for lunar photography determines the exposure times due to the varying brightness phases of the moon. The higher the speed (ISO) of the film, the shorter the exposure. The drawback of using super high speed films such as the ISO 3200 is that the finished pictures tend to be very grainy especially when enlarged. The following table gives the exposure times (in seconds) for various speed films at different phases of the moon. Due to atmospheric turbulence and light pollution, it is best to 'bracket' your exposures. Bracketing consists of taking exposures on both sides of the recommended shutter speed."

http://home.hiwaay.net/~krcool/Astro/moon/howtophoto/index.htm

Also, try to shoot when the moon is no lower than 30* elevation above horizon. Anything you can do to cut down on vibration during exposure (remote release, mirror lockup, hat trick shutter, wind shelter) would be helpful.