Transferring to a new PhD program Last year, I applied to several astronomy PhD programs in the United States, and ended up attending a certain institution with a pretty good reputation in the field. However, in the eight months since I've applied, I've come to realize that this is not the discipline I wish to pursue for a career for a variety of reasons. Instead, I would like to pursue the field of condensed matter physics, which has many more applications. Unfortunately, these two fields are different enough that they have two separate programs at many universities, including the one I am currently enrolled in.

To make this career goal attainable, I thus need to transfer to a different PhD program. If I were to apply to my own university again, I would have no competitive advantage from what I have heard. So far, I've identified around ten different programs where I could see myself ending up. I graduated summa cum laude from my undergrad institution with a major relevant to both fields, have significant research experience (albeit in my old subject area rather than my new one), and my general and subject GRE scores are great as well. The only issue is transferring itself. Would potential institutions look unfavorably on my application since I am already in a grad program elsewhere? Is my plan feasible?

Any information/advice would be greatly appreciated!
I doubt that it would have any effect. People learn and change and others recognize that. However, the only way to know is to actually apply, or at least make contact with some of the other universities. 

You will want to be able to explain your reasons, of course, and be pretty sure you aren't making a mistake by changing. 

But you don't have to abandon your current studies to explore other opportunities. Find and contact a professor or two in the new discipline and ask them if you would be a good candidate in their program, or even working under their direction. You could also just make application a few places. 

However, if you are currently funded, and/or other people are depending on your research to complement theirs, you will need to deal with the consequences of that so that you don't put yourself or others at a disadvantage. 

But, as you are early in your studies, I don't really see much of a problem. Just ask at the institutions you are considering.