Question: how to connect two eyepieces together with the x3 Barlow lens

I have 10mm,25mm, and x3 Barlow. Is there any way to connect them together to archive the maximum magnification of 105mm?

Answer: 
I'm not an expert, but I looked into this recently when toying with the idea of a scale model of the observable universe. To the best of my understanding, the following is approximately correct.

TLDR: The expansion happens on the very large scale of the universe. At the scale of the observable universe the Andromeda galaxy is a next-door neighbour, and at the local scale gravity is strong enough to override any effect of expansion.

The Milky Way is 100,000 light years across, 2.5 million light years brings us to the Andromeda galaxy. 

Galaxies cluster in galaxy groups, and 10 million light years span about 50 galaxies and brings us to the edge of what's called the Local Group. 

Galaxy groups cluster into superclusters. We're part of the [Laniakea Supercluster](https://www.space.com/27016-galaxy-supercluster-laniakea-milky-way-home.html), which spans about 100,000 galaxies and 500 million light years. 

For any appreciable expansion (redshift 0.1) you need at least a billion light years. It's something that happens in the voids between superclusters, and doesn't become really pronounced until you're halfway across the observable universe (redshift 1, 7-8 billion light years as measured in light travel time).

For the "raisins in a loaf" analogy, I think it's not too wrong if you think of the raisins as superclusters rather than individual galaxies. Note that although the dough expands in a baking loaf, individual raisins do not, because there are other forces at work that hold them together.
Just as molecules in the bread have random motion due to heat, galaxies have random motion due to variations in the initial state of the universe. For galaxies that are close by, those variations are smaller than the Hubble expansion, and the Hubble expansion is simply a *general trend*; object that are farther away from us tend to, *on average*, be moving away from us at higher speed, but individual objects can still be moving towards us.

According to [this site](http://w.astro.berkeley.edu/~mwhite/darkmatter/hubble.html), the Hubble constant is "around 70 kilometers per second for every megaparsec in distance". According to [wikipedia](https://en.wikipedia.org/wiki/Andromeda_Galaxy), Andromeda is "780 kiloparsecs" away. Multiplying those together, we get that Andromeda's movement due to the Hubble expansion should be about 5 km/sec. Wikipedia also says that "The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres per second". That means that Andromeda's motion due to Hubble expansion is about 4% of its total movement. Andromeda has so much velocity relative to Earth that the Hubble expansion simply gets drowned out.