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Hi Peter,
There is no formal way to say 'how far ' can we see. Instead with a scope it is 'how dim' can we see.
The distance to visibility relationship is a tenuous one. There are objects in the sky thst are increadibly bright and far away that we can see. Others dim but much closer and look as bright as the former.
This is also twisted even further if you add photography into the equation, and the technological advances that continuously allow small apertures image fainter and fainter objects.
Visually, the 'furthest' object we can see are a pair of Quasars. The brighest of these sits around magnitude 13 (if I remember correctly) - well within the capacity of your 10". Quasar 3C 273 punches out from 2.5billion light years. It sits in the constellation Virgo. The next brightest needs much larger apertures.
There is a 'formula' to determine the faintest a given aperture can see. Actually there is a few. These on the most part give a value of 'faintest' as these equations just about all assume perfect optics, perfect atmospheric conditions & perfect human eyes with no degradation from age or illness. Another assumption these equations make is the light source is a point, not an extended object, like a galaxy - the magnitude value given to extended objects like clusters, galaxies and nebulae, us their cumulative magnitude, meaning that all the light from the extended object were put into a single point source. So if you calculate a limiting magnitude of say 15 for your scope, you pretty much have no chance of seeing a magnitude 15 galaxy as its light is spread out.
There are several sites that will calculate the limiting magnitude of a scope. Some are beter than others as the will include parameters such as optical quality and cleanliness, observer's age and experience, and the such. Do a search to find these. Some planetarium phone apps also gave similar functions.
So to strictly answer your, how far we can see is 2.5 billion lightyears, with a bloody big gap between this object and everything else in between, which visually maxes out at around 200 million lightyears, which is much fainter than mag 13 of 3C 273.
Mental.
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