This page is under construction, even moreso than the rest of this site!
This page goes into more technical detail about optical considerations when using night vision for astronomy. The reason I put this separate page together is because night vision actually is a different paradigm for observing, and a lot of things we consider to be constants in non-amplified astronmy all become variables that can be traded off.
Fundamentally, astronomers are plagued by a lack of signal-to-noise ratio in the starlight that reaches us here on planet Earth. Prior to the use of light amplification, there is a very simple, fixed equation: more light, more better. To get more light, you have to get more aperture, and/or faster focal ratio. But larger aperture means smaller field of view, and this actually limits you from being able to appreciate some of the beautiful wide-field nebula.
At a high level, I have found myself thinking much more intentionally about focal ratio and fields of view than ever before, especially as a visual astronomy guy (and not an astrophotographer).
It has been remarked that night vision causes a shift from "single telescope, multiple eyepieces" to "single eyepiece, multiple telescopes". I personally found this to be the case, and the transition happened quickly. I didn't want to be observing through any eyepiece except my night vision device, and therefore to look at different things, I needed to swap out the objective, or play with barlows and focal reducers.
This also leads down the path of looking for alternative lenses to use, in order to achieve the right balance of light-gathering power, magnification, and optical quality (e.g. lack of coma, abberation, etc.).
TODO: Pull information from this thread: http://www.cloudynights.com/topic/545232-observations-on-an-adjustable-magnification-night-vision-setup/