The idea that you can make deep-sky (faint objects) more visible by increasing magnification (and decreasing exit pupil) has been circulating for sometime. The idea is that increasing magnification will darken the sky background, thereby making faint objects stand out more. How much truth is there to this notion?
In my experience, it does work - sometimes. In other words, it is like many other observing techniques. It works, but not all of the time. There are simply too many variables in observing for a one-size fits all approach. I've had my best luck with this when observing with large telescopes. Large apertures give you more light to work with and using a telescope gives you access to many different magnification and eyepiece options. Typically, I've found there will be one combination of magnification and telescope aperture that gives the "best" contrast between the sky background and the object and that, true to form, this is sometimes at surprisingly high magnifications. Of course, this is sometimes at lower magnifications, too. It depends on so many things - the type of object, it's magnitude, your telescope, your eyepieces, your skill as an observer and, perhaps most importantly, observing conditions. We all know those change night by night and even hour by hour. Then, too, what constitutes "best" in terms of contrast is largely subjective. It's as much your call as much as it is the next observer's.
Next, I will look at this notion of increasing magnification to darken sky background and apply it to binoculars.
Joanie
